Students

Supplementary Questions

Chapter 1

  1. The central focus of a new conference centre is a square composed of one-metre square marble tiles.
    1. If the designer wants the platform to measure 14 metres by 14 metres, how many one-metre tiles will be required?
    2. If the budget is sufficient for only 175 of these tiles and the tiles cannot be cut, what are the dimensions of the largest square platform that can be assembled?
  2. A third of a percent of the population of Glasburgh and a quarter of a percent of the population of Edingow record their occupation as ‘company director’. If the populations of Glasburgh and Edingow are three quarters of a million and 900,000 respectively how many company directors reside in each place?
  3. A visitor to Britain from Bahrain wants to buy some articles of clothing in a department store in London. He selects a man’s jumper costing £29.99, a lady’s cardigan that costs £34.99, and a pair of men’s shoes for £49.99. A large sign in the store says that visitors from abroad can buy goods ‘VAT-free’. The prevailing rate of VAT is 20%. How much will he be charged for these goods?
  4. An electricity supplier charges domestic consumers a fixed quarterly fee of £8.50 for maintaining the supply and 16.35 pence for each unit of electricity consumed. The total amount is then taxed at 5 per cent. A householder uses 829 units of electricity in a quarter, how much will they be charged, including tax?
  5. In one month consumers purchased 58749517 litres of bottled still mineral water. Of this total, sales of the three largest suppliers, in litres, were:
  6. Vodder

    6602362

    Aquaria

    5191584

    Lake

     4051948

    1. Specify the total sales and the sales of each of the suppliers to
      1. four significant figures
      2. two significant figures
  7. Specify the market share of each of the suppliers to two decimal places.

Chapter 2

  1. A machine vending company operates three hot drinks machines, one at a bus station, another at a train station, and the third at a leisure centre. The number of coffee, tea, and chocolate drinks dispensed from each in a single day is given in the following table.

    Location of machine

    Number of drinks

     

    Coffee

    Tea

    Chocolate

    Bus station

    68

    91

    23

    Train station

    105

    74

    47

    Leisure centre

    49

    67

    89

    1. Plot a component bar chart to represent these figures.
    2. Plot a cluster bar chart to represent these figures.
  2. The ages of 28 applicants for a graduate management trainee post are:

    21

    23

    21

    21

    23

    21

    24

    22

    21

    24

    21

    26

    23

    22

    21

    22

    23

    21

    22

    21

    22

    25

    21

    22

    21

    22

    21

    24

    1. Produce a frequency distribution for these figures.
    2. Plot a bar chart to represent the frequency distribution.
  3. The rates of growth in revenue (%) of 25 leading companies over a year were:
  4. 4.22

    3.85

    10.23

    5.11

    7.91

    4.60

    8.16

    5.28

    3.98

    2.51

    9.95

    6.98

    6.06

    9.24

    3.29

    9.75

    0.11

    11.38

    1.41

    4.05

    1.93

    5.16

    1.99

    12.41

    7.73

    1. Compile a grouped frequency distribution for these figures.
    2. Construct a histogram to portray the distribution.
  5. The prices of 11 detached houses for sale in a small country town in the UK and the numbers of bedrooms in them are:

    Price (£000)

    185

    190

    225

    249

    295

    300

    320

    365

    400

    560

    640

    Bedrooms

    2

    3

    2

    3

    3

    4

    3

    4

    5

    4

    6

    1. Plot a scatter diagram to portray these figures.
    2. Describe the relationship between the two variables.
  6. Quarterly sales of gloves (in thousands of pairs) achieved by an online retailer over three years were:
    Year

    Quarter

     

     

     

     

    1

    2

    3

    4

    1

    23.0

    5.5

    0.6

    17.7

    2

    22.1

    6.3

    1.1

    19.8

    3

    24.2

    7.2

    0.9

    16.9

    Produce a time series plot to represent this data.

  7. The CO2 emissions recorded, in grams per kilometre, for 18 entry-level petrol-driven models of family car were:

    112

    108

    132

    99

    114

    123

    152

    119

    136

    134

    129

    94

    125

    120

    108

    112

    103

    108

    1. Compile a stem and leaf display of these data.
    2. Using the same set of stems to produce a back-to-back display, with the CO2 emissions of the 18 entry-level petrol-driven models of small car (below) to the left of the stems and use it compare the two distributions.

    102

    95

    99

    101

    114

    117

    114

    111

    124

    105

    115

    95

    127

    118

    110

    95

    125

    108

Chapter 3

  1. A supermarket sells kilogram bags of apples. The numbers of apples in 22 bags were
  2. 7

    9

    8

    8

    10

    10

    8

    10

    10

    8

    8

    10

    7

    9

    9

    9

    7

    8

    7

    8

    9

    8

    1. Find the mode, median and mean for this set of data. Compare your results.
    2. Plot a simple bar chart to portray the data.
  3. A supermarket has one checkout for customers who wish to purchase 9 items or less. The numbers of items presented at this checkout by a sample of 19 customers were:
  4. 5

    8

    7

    7

    6

    6

    10

    8

    9

    9

    9

    6

    5

    9

    8

    9

    5

    5

    6

    1. Find the median and quartiles for this set of data.
    2. Determine the semi-interquartile range.
    3. Calculate the mean and standard deviation for this set of data.
  5. Two neighbours work at the same place. One travels to work by bus, the other cycles to work. The times taken (in minutes) by each to get to work on a sample of 8 days were:
  6. Bus passenger

    33

    28

    40

    32

    41

    32

    38

    42

    Cyclist

    26

    33

    27

    31

    31

    30

    28

    24

    Calculate the mean and standard deviation for each set of times and use them to compare the travel times for the two commuters.

  7. The amounts (in pounds) spent in a month by 42 shoppers on hair-care products were
  8. 13.23

    11.19

    14.49

    6.51

    10.07

    18.91

    13.14

    15.90

    16.11

    12.89

    9.12

    12.27

    8.16

    10.84

    9.33

    10.36

    15.02

    8.45

    12.92

    6.79

    13.02

    6.85

    13.76

    8.92

    11.40

    10.88

    8.99

    9.46

    8.67

    8.52

    11.17

    5.79

    9.17

    9.16

    5.24

    7.11

    7.37

    10.60

    13.21

    10.61

    4.65

    8.94

    Construct a boxplot to represent this set of data.

  9. An insurance company recorded the time in seconds that a sample of 79 callers trying to contact It by phone had to wait. After introducing a new system, the company recorded the waiting times for each of a sample of 61 callers. The results are in the following grouped frequency distributions:
  10. Waiting time (seconds)

    Frequency (before change)

    Frequency (after change)

    0 and under 10

     2

     7

    10 and under 20

    15

    19

    20 and under 30

    23

    31

    30 and under 40

    24

     3

    40 and under 50

    11

     1

    50 and under 60

     4

     0

    1. Determine values for the mean and median of the distributions.
    2. Find an approximate value for the standard deviation of each distribution.
    3. Use the figures you obtain for (a) and (b) to compare the two distributions.

Chapter 4

  1. The outstanding balances on the monthly bills of 12 credit card accounts (in £) and the annual income of the account holders (in £000) are:
  2. Balance

    250

    1630

    970

    2190

    410

    830

    0

    550

    0

    682

    0

    0

    Income

    15

    23

    26

    28

    31

    35

    37

    38

    42

    42

    45

    46

    1. Portray the data on a scatter diagram with Balance as the dependent variable.
    2. Calculate the correlation coefficient and comment on its value.
  3. In a survey of commuting patterns ten respondents say that they cycle to work. The distances they travel (in miles) and the mean journey times (in minutes) they report are:
  4. Distance

    2

    2

    3

    4

    5

    6

    7

    8

    8

    10

    Mean journey time

    10

    15

    15

    20

    25

    25

    30

    40

    45

    50

    1. Portray the data on a scatter diagram.
    2. Calculate the slope and intercept of the line of best fit using simple linear regression analysis.
    3. Plot the line of best fit and use it to estimate the time that a journey of 9 miles would take.
  5. The classified advertisement columns of a local paper contain details of twelve used cars of a particular make and model. The prices of these cars (in £000) and the numbers of miles they have travelled (in 000) are:
  6. Price

    6.8

    6.2

    5.7

    4.7

    6.0

    5.9

    7.0

    4.5

    5.0

    3.0

    3.8

    3.5

    Mileage

    9

    13

    11

    33

    14

    11

    3

    19

    22

    35

    40

    44

    1. Present these figures in the form of a scatter diagram.
    2. Find the least squares line of best fit and plot it on your scatter diagram.
    3. Predict the price of a car of this type that has travelled 25 000 miles.
  7. The turnover figures provided in the annual accounts of an online retailer over the five years from 2014 to 2018 were:
  8. Year

    2014

    2015

    2016

    2017

    2018

    Turnover (£m)

    7101

    7350

    7844

    8249

    8598

    The values of the Retail Price Index (RPI) for this period were:


    Year

    2014

    2015

    2016

    2017

    2018

    RPI

    256.0

    258.5

    263.1

    272.5

    281.6

    Use the RPI values to deflate the turnover figures so that they are all expressed in 2014 pounds.
    (Source of RPI figures: ‘Retail Price Index’, Office for National Statistics. Contains public sector information licensed under the Open Government Licence v3.0.)

  9. A textile manufacturer makes casual jackets. The company buys lining fabric, interfacing fabric and outer fabric. They cut and machine the fabrics to make the garments. The prices per metre of these materials in 2017, 2018 and 2019 were:
  10.  

    Year

    Fabric

    2017

    2018

    2019

    Lining

    £2.20

    £2.30

    £2.35

    Interfacing

    £0.92

    £0.95

    £1.00

    Outer

    £6.50

    £7.25

    £7.95

    In 2017 the company purchased 2500 metres of lining fabric, 400 metres of interfacing fabric, and 2750 metres of outer fabric. In 2018 these quantities were 2800, 500, and 3200 respectively. In 2009 they were 3000, 500, and 5000 respectively.

  11. The HR department at Adastra Aerospace records staff absences at its manufacturing plant, which works a five-day week. In the last three weeks the absences were:
  12. Week

    Monday

    Tuesday

    Wednesday

    Thursday

    Friday

    1

    15

    8

    6

    10

    24

    2

    14

    6

    5

    12

    19

    3

    17

    9

    8

    11

    22

    1. lot the series and calculate five-point moving averages.
    2. Estimate daily components for the series.
    3. Produce estimates for the values of the trend in week 4 using regression analysis.
    4. Compile forecasts for the number of absence the company should expect each day in week 4.

Chapter 5

  1. Since it was set up 73825 people have visited the website of a fashion designer and 6301 of them purchased goods online. When someone visits the site what is the probability that:
    1. they do not purchase goods on-line?
    2. they do purchase goods on-line?
  2. Last year 12966 people opened new accounts at a building society. Of these 5314 were branch-based accounts, 4056 were postal accounts, and 3596 were Internet accounts. What is the probability that when a customer opens a new account:
    1. It is a postal account?
    2. It is an Internet account?
    3. It is either branch-based or postal?
  3. A safety agency analysed road traffic accidents involving injury to pedestrians by private cars and produced the following table:

  4. Degree of injury

    Type of car

     

    4×4

    Sports

    Other

    Fatal

    8

    5

    14

    Serious

    21

    9

    38

    Non-serious

    13

    7

    95

    What is the probability that:

    1. An injury to a pedestrian proves fatal?
    2. An accident involved a sports car?
    3. An accident involved a 4×4 car or resulted in a non-serious injury?
    4. An accident resulted in serious injury and involved an ‘other’ type of car?
    5. An accident that involved a 4×4 car resulted in a fatal injury? Compare this figure and your answer to (a), and comment on whether the type of car and degree of injury are independent.
  5. You win a prize in a charity raffle. The prize, donated by a hotel company that runs three aging hotels, is a voucher entitling you to a free double room for a weekend at each of the three hotels in the chain, the Xerxes, the York and the Zetland. The manager of each hotel will pick the room you stay in at each hotel at random. The Xerxes has 12 double rooms, 7 of which are en suite. The York has 28 double rooms, 16 of which are en suite. The Zetland has 18 double rooms, of which 13 are en suite.
    1. What is the probability that none of the rooms you get is en suite?
    2. What is the probability that one of the rooms you get is en suite?
    3. What is the probability that two or more of the rooms you get are en suite?
  6. As a result of flood damage a supermarket has a very large stock of tins without labels. Forty per cent of the tins contain soup, 30% contain carrots, 25% contain raspberries, and 5% contain asparagus. The tins are to be offered for sale at three for 50 pence. When a customer buys three tins what is the probability that:
    1. None of the tins contain asparagus?
    2. All three tins contain soup?
    3. One tin contains raspberries?
    4. Two tins contain carrots?
    5. The contents of the three tins are different?

Chapter 6

  1. The employees of the Brecht Bank decide to put on a five-a-side football tournament to raise money for charity. If the teams are chosen at random and four tenths of the employees are women, what is the probability that:
    1. A team consists entirely of males?
    2. There are three females in a team?
    3. There are three or fewer females in a team?
    4. The majority of a team are female?
  2. An egg-packing company thinks that a tenth of all the eggs they buy from farms are contaminated with harmful bacteria that could result in food poisoning. What is the probability that in a pack of ten eggs:
    1. None of the eggs contain harmful bacteria?
    2. More than two eggs contain harmful bacteria?
    3. Half the eggs contain harmful bacteria?
    4. Less than two eggs contain harmful bacteria?
  3. An office worker receives an average of 22.5 e-mail messages per day. If his working day lasts seven and a half hours, what is the probability that:
    1. He receives no e-mails in an hour?
    2. He receives one e-mail in an hour?
    3. He receives two or fewer e-mails in an hour?
    4. He receives more than four e-mails in an hour?
  4. A pharmaceuticals company marketed a drug that proved to be an effective treatment but unfortunately resulted in side effects for some patients. On the basis of initial clinical research the probability that a patient who is treated with the drug suffers no side effect is 0.85, the probability of a minor side effect is 0.11, and the probability of a major side effect is 0.04. Under an agreement with the appropriate authorities the company has agreed to pay £2500 in compensation to patients who suffer a minor side effect and £20 000 in compensation to patients who suffer a major side effect.
    What is the expected value of the compensation per patient?
  5. An arable farmer is thinking of sowing scientifically modified crops next year. She believes that if she did so her profits would be £75 000, compared to £50 000 if she sowed unmodified crops. A neighbouring organic farmer has made it clear that if his crops are contaminated he will demand compensation. The arable farmer guesses that the probability of contamination to be 40%. In the event that the neighbouring farmer claims compensation there is a 30% chance that the arable farmer would have to pay £25 000 in compensation and a 70% chance she would have to pay £50 000 in compensation.
    1. Construct a decision tree and use it to advise the arable farmer.
    2. An expert puts the probability that there will be contamination of the crops of the neighbouring farmer at 60%. Should the arable farmer change her strategy in the light of this information?

Chapter 7

  1. A bed linen company manufactures duvets that have a mean TOG rating (a measure of thermal effectiveness) of 11.5 with a standard deviation of 0.18. If the TOG ratings are normally distributed,what is the probability that a duvet selected at random has a TOG rating:
    1. Above 12?
    2. Above 11.3?
    3. Below 11.6?
    4. Below 11.1?
    5. Between 11.2 and 11.4?
    6. Between 11.5 and 11.9?
  2. The amount of time that visitors to a web site browse the site is assumed to be normally distributed with a mean of 8.75 minutes and a standard deviation of 3.1 minutes. What is the probability that a randomly selected visitor browses the site for:
    1. Less than 5 minutes?
    2. More than 10 minutes?
    3. Less than 15 minutes?
    4. Between 3 and 7 minutes?
    5. Between 10 and 14 minutes?
    6. Between 8 and 12 minutes?
  3. A large company insists that all job applicants who are invited for interview take a psychometric test. The results of these tests follow the normal distribution with a mean of 61 points and the standard deviation of 7.2 points.
    1. What proportion of applications would be expected to score over 70 points?
    2. What proportion of applications would be expected to score under 40 points
    3. What proportion of applications would be expected to score between 50 and 65 points?
    4. What score is exceeded by 20% of applicants?
    5. What is the highest score achieved by the 5% of applicants who do least well in the test?
  4. The mean legal lifetime (the number of miles travelled before the tyre is worn down to the legal limit) of car tyres of a certain brand is 23,450 miles. The standard deviation is 1,260 miles. If the lifetimes of the tyres are normally distributed, what is the probability that a random sample of four tyres fitted to a vehicle will have a mean legal lifetime of:
    1. More than 25,000 miles?
    2. More than 22,000 miles?
    3. Less than 24,000 miles?
    4. Less than 23,000 miles?
    5. Between 22,500 and 24,500 miles?
    6. Between 23,400 and 24,200 miles?
  5. The delays to scheduled airline departures at an international airport are known to follow a skewed distribution with a mean of 11 minutes and a standard deviation of 7 minutes. What is the probability that the mean delay of a random sample of 40 flights is:
    1. More than 12 minutes?
    2. More than 10 minutes?
    3. Less than 8 minutes?
    4. Less than 11 minutes?
    5. Between 9 minutes and 10.5 minutes?
    6. Between 11.5 and 12.5 minutes?
    7. Between 9.5 and 14 minutes?
  6. Ramblers sell their crisps in multipacks of 12 bags. The contents of the individual bags are normally distributed with a mean of 25 grams. The contents of each bag in one multipack were measured and the standard deviation found to be 0.5 grams.
    1. What mean weight of bags in multipacks will be exceeded by 10% of packs?
    2. What mean weight of bags in multipacks will be exceeded by 5% of packs?
    3. What mean weight of bags in multipacks will be exceeded by 1% of packs?

Chapter 8

  1. The burning times of aromatherapy candles are known to be normally distributed with a standard deviation of 6 minutes. The mean burning time of a random sample of 18 candles was 3 hours 51 minutes. Set up:
    1. A 90% confidence interval for the mean burning time of the candles.
    2. A 99% confidence interval for the mean burning time of the candles.
  2. The distribution of rents of flats in a city is known to be a skewed with most flats being relatively cheap to rent but some, in prestige blocks, very expensive. The mean rent of a sample of 48 flats was £403 per month with a standard deviation of £65.
    1. Construct a 90% interval estimate of the mean rent of two-bedroom flats in the area
    2. The population standard deviation turns out to be £59. In the light of this new information, determine the size of sample necessary to enable the mean rent to be estimated to within £10, in other words for the error to be £10, with a 90% level of confidence.
  3. The weights of bags of pears sold to customers asking for one pound of pears at a market stall are known to be normally distributed. The weights of bags served to a random sample of 15 customers were measured. The sample mean weight was 1.06 lb with a standard deviation of 0.11 lb.
    1. Produce a 95% confidence interval for the weight of ‘one pound’ bags of pears.
    2. Produce a 99% confidence interval for the weight of ‘one pound’ bags of pears.
  4. In a UK survey of a random sample of 281 working women who had children, 175 reported that they felt that having children had held back their career prospects. In a similar study of 138 women in Denmark, 65 reported that having children had held back their career.
    1. Produce a 95% confidence interval for the proportion of women in the UK who consider that having children held back their career prospects.
    2. Produce a 95% confidence interval for the proportion of women in Denmark who consider that having children held back their career prospects.
    3. How do the two confidence intervals compare?
  5. Office workers at a large organization are told that they should not work for more than one and a half hours at their PCs before taking a break. A survey of a random sample of 37 employees found that the mean time that they worked at their PCs before taking a break one morning was one hour 43 minutes with a standard deviation of 18 minutes. Test the hypothesis that on average the employees of this organization are working for no more than one and a half hours before taking a break using a 1% level of significance.
  6. 6. In an advertisement it is claimed that a brand of domestic air freshener will last on average at least 70 days. The mean and standard deviation of the lifetimes of a sample of 19 air fresheners were 69.3 days and 2.9 days respectively.
    1. Test the claim made for the product using a 5% level of significance.
    2. What assumption must be made for the test to be valid?
  7. A bus company claims that the mean journey time for the service from Paglashonny to Gorley is 53 minutes. A random sample of 35 journeys was chosen and each journey timed. The mean journey time of these journeys was 57 minutes with a standard deviation of 4.6 minutes.
    1. Test the bus company’s claim at the 5% level of significance and comment on the result.
    2. It appears that for nine of these journeys the regular driver was absent from work through illness and relief drivers, who were unfamiliar with the route, had to be used. The mean journey time for the remaining journeys was 55 minutes with a standard deviation of 3.1 minutes. Test the bus company’s claim again at the 5% level of significance using these figures and comment on the result.
    3. What do you need to assume about the population of journey times for the results from the second test to be valid?
  8. Last year 61% of total job applications received by a national recruitment agency were from female applicants. Out of a random sample of 192 applications received this year, 105 were from females. Test the hypothesis that the proportion of applications from females has not changed using a 10% level of significance.

Chapter 9

  1. A random sample of 120 employees at a large office complex were asked how they travelled to
    work and whether they considered there were enough car parking spaces at the complex.
  2.  

    Mode of travel

     

    Car

    Other

    Enough parking spaces

    27

    23

    Not enough parking spaces

    53

    17

    Test the hypothesis that there is no association between mode of travel and opinion on parking places:

    1. At the 5% level of significance.
    2. At the 1% level of significance.
  3. A survey of a random sample of 320 pet owners undertaken by a petfood manufacturer yielded the
    following data about type of pet and size of household:
  4.  

    Type of household

    Pet

    Single person

    Couple

    Family

    Dog

    31

    40

    55

    Cat

    67

    17

    12

    Other

    52

    13

    33

    1. Using a 1% level of significance test for association between type of pet and type of household.
    2. Examine the components of the test statistic and comment on the patterns they reveal.
  5. The correlation coefficient between the percentage increase in profits and the percentage increase in share price on the day the profits were announced for a random sample of 19 publicly quoted companies was +0.490. Test the hypothesis of no positive correlation at the 5% level of significance.
  6. An HR consultant undertook a survey of a random sample of 52 employees of a large bank. She found a correlation coefficient of –0.377 between the satisfaction level reported by employees and the length of service they had achieved. Test the hypothesis that there is no significant negative correlation at the 1% level.
  7. 5. An auctioneer has recorded the profit made at a random sample of eight auctions and the number of people attending each of them.

  8. Attendance

    100

    120

    140

    250

    420

    470

    580

    650

    Profit (£)

    275

    192

    380

    372

    518

    611

    546

    973

    1. Find the regression equation and test the hypothesis that the population slope is zero at the 5% level of significance.
    2. Produce a 95% confidence interval for the mean profit from auctions that attract 300 people.
    3. Produce a 95% prediction interval for the profit that can be expected from a single auction that attracts 300 people.