(a) Selecting random numbers using excel

(b) Probabilistic sample selection

(c) Snowballing

(d) Downloading secondary data

(e) Selecting a population

2) ‘Stratified sampling’ may provide greater precision of population estimates, compared to ‘simple random sampling’ because it

(a) only applies to collecting secondary data

(b) requires the whole population to be sampled

(c) makes use of supplementary information

(d) always divides the population into geographic areas

(e) all of the above

Data for questions 5, 6 and 7

The data below describes the test marks from a class of fifteen students. They represent the marks from the full group, ie the total population. Use this data for questions 5 and 6 and 7.

Marks: 38, 60, 63, 45, 47, 45, 72, 75, 31, 51, 72, 66, 62, 54, 59.

5) Are the population mean and the median (to 2dp):

(a) 56 and 56.5

(b) 56 and 59

(c) 58 and 59.5

(d) 58 and 60

(e) None of the above

Continued…

6) Are the range and the average deviation (to 2dp):

(a) 44 and 0

(b) 44 and 10.8

(c) 37 and 0

(d) 75 and 10.8

(e) None of the above

7) Are the standard deviation and coefficient of variation from this population (to 2 dp):

(a) 12.61 and 0.23

(b) 12.61 and 4.44

(c) 13.05 and 0.23

(d) 13.05 and 4.29

(e) None of the above

8) A population was found to have a standard deviation of 3, a mean of 14, a mode of 8, and a median of 10. Is the frequency distribution:

(a) Positively skewed

(b) Negatively skewed

(c) A completely symmetrical distribution

(d) Bimodal

(e) Cannot be described without further information

Use the data below for questions 9, 10, 11 and 12. The data describes the ages of the whole population on a mailing list. It is being evaluated by a company that is considering buying the list.

The ages (in years) of the 50 individuals on the mailing list, in ascending order are:

10,11,13,14,14,15,15,17,18,20,20,21,22,24,26,26,26,27,29,30,31,31,33,34,36,36,36,37,38,

39,40,41,41,43,44,45,45,46,47,48,49,51,53,55,57,58,59,59,60,60.

These 50 ages average 35.

9) Is the variance of this raw data (to two decimal places):

(a) 14.86

(b) 216.4

(c) 220.522

(d) 10820.0

(e) none of the above

Put the raw data into class intervals of:

Class Mid Point (xi)

0 -< 16 12

16 -< 21 18.5

21 -< 30 25.5

30 -< 40 35

40 -< 60 50

> 60 65

10) Is the mean of the grouped data (to 2 dp):

(a) 8.63

(b) 35.0

(c) 35.54

(d) 206.0

(e) None of the above

11) You wish to consider the accuracy of your estimate in the previous

question. The percentage error for the estimate of the mean of the

grouped data is (to 2 dp):

(a) – 0.54%

(b) – 0.2

(c) 0%

(d) + 0.02%

(e) None of the above

12) Is the median of the grouped data (to2 dp):

(a) 32.17

(b) 35.32

(c) 35.91

(d) 45.91

(e) None of the above

13) When calculating the median from grouped data which of the

following is assumed:

(a) All observations are integers

(b) All observations are spread evenly throughout their class

(c) All classes are of the same width

(d) All classes are of different widths

(e) All observations are located at the class mid point

14) For a standard normal (Z) variable ie. Z~N(0,12), p(1.6<Z<1.8) is (to accuracy of 4dp):

(a) 0.0189

(b) 0.4811

(c) 0.5189

(d) 0.9093

(e) None of the above

15) For a standard normal (Z) variable ie. Z~N(0,12), p(Z > -2.22) is (to accuracy of 4dp):

(a) 0.0132

(b) 0.4861

(c) 0.4868

(d) 0.9861

(e) 0.9868