Thread: practice exam for future students, need help to make sense.

1
) a) The following table is intended to present five figure summaries [maximum, third
quartile, median, first quartile, minimum] of sets of data. Which two columns contain errors?
(3 marks)
A B C D
Max
125.0 60 9.76 20
Q3
47.3 17 6.84 8
Median
53.3 10 5.11 5
Q1
24.3 6 3.45 1
min
19.2 3 6.14 0
b) The following table is intended to present three figure summaries [ ( mean + sd), mean,
and (mean - sd) ] of sets of data. Which two columns contain errors?
(3 marks)
A B C D
mean +sd
7.33 6.68 31.18 7.73
mean
4.58 4.06 16.00 3.30
mean-sd
1.28 1.44 0.82 1.86
c)
A researcher who is interested in visual skills assesses 21 volunteer participants using a
simple ball control task. Each participant bounces a foam football on their fist. For a single
observed trial, the researcher records the number of bounces they achieve before losing
control of the ball. The scores recorded are given below.
10 38 17 4 35 33 7
35 8 8 12 7 3 13
4 60 5 15 11 6 5
Table 1
Ball skills assessment: scores for 21 Participants.
Give the mean, standard deviation, median and quartile points of these values.
(NB the sets of summary values given in parts a and b include the required values.)
(5 marks)
d)
Present a graph showing a three figure summary and the five figure summary on the same
axes. ( 7 marks)
e)
Which of these two representations of this data would you choose to use in a formal report?
Briefly, give a reason for your choice. (3 marks)
f)
A colleague of the researcher points out that the distribution of values is skewed. More
sensitive statistics can be applied to variables that are not skewed. How would you advise
the researcher to develop their test?
(4 marks)
2
) Data for the performance of a sample of 18 students on a research methods course are
tabled below. The course assessment consists of two components a statistics test and a set of
reports.
Student Stats Pracs
a 14 11
b 28 28
c 45 37
d 48 53
e 51 43
f 55 58
g 56 58
h 59 59
i 61 43
j 61 46
k 62 58
l 65 57
m 66 47
n 67 59
n 68 50
p 69 40
q 78 59
r 82 62
a) Draw a scattergram to show the trends. (8 marks)
b) Which of the following values is closest to the Pearson product moment correlation
coefficient? (2 marks)
-0.203 0.008 0.416 0.806 0.952 1.203
c) Assuming the correlation coefficient is tabled above, what conclusion is supported?
(3 marks)
d) The lecturer then re computes the correlation coefficient with the data for two students
with low grades omitted. Which tabled alternative value is then closest to the computed
value?
(2 marks)
Selected critical values of the Pearson Product
Moment Correlation Coefficient.
2 tailed probability:
N of Pairs 0.10 0.05 0.02 0.01
14
0.458 0.532 0.612 0.661
16
0.426 0.497 0.574 0.623
18
0.400 0.468 0.543 0.590
20
0.378 0.444 0.516 0.561
22
0.360 0.423 0.492 0.537
24
0.344 0.404 0.472 0.515
e) Comment on the change in the result that occurs when the sample is reduced. (4 marks)
f) Suggest an alternative analysis that may have been used. (3 marks)
g) What should be considered as relevant to the choice of test? (5 marks)
3)
Do women smile more than men?
Following an agreed protocol, 62 students each observe 8 pairs of people. At the time each
pair is in conversation in a public place. One person in each pair is covertly and carefully
observed for a period of just 10 seconds. The students select their pairs so that they each
observe 8 pairs of people, 2 of each of the possible combinations. [Male observed with a
female companion, Male observed with a male companion, Female observed with a male
companion and Female observed with a female companion.] The collated data are shown in
the table:
Sex of Observed P F F M M
Sex of companion f m f m Totals
N smiling 87 72 79 54 292
N not smiling 37 52 45 70 204
Total 124 124 124 124 496
Use this data to complete the 2x2 table below.
Observed Frequency F M Total
N smiling 292
N not smiling 204
248 248 496
a) What hypothesis is tested when a 2x2 Chi square is used to assess the trend shown in this
table?
(3 marks)
b) How many degrees of freedom are associated with the relevant critical value?
( 2 marks)
c) If there is no difference between the proportion of men and women smiling, how many
would there be in each cell?
(4 marks)
d) What is the difference between the observed and expected frequencies in each cell?
(NB with a single degree of freedom all differences are the same size. The total for each row
and column is zero.)
(2 marks)
Observed - Expected F M Total
N smiling 0
N not smiling 0
0 0 0
Expected Frequency F M Total
N smiling 292
N not smiling 204
248 248 496
e) Confirm the two given values as
(O-E)*(O-E) / E and complete the table.
What is the total Chi Squared value?
(5 marks)
Observed F M Total
(O-E)*(O-E)/ E 1.16
(O-E)*(O-E)/ E 1.66
f) What conclusion would you expect in a formal report of this study?
(3 marks)
g) Give one guideline that would help a student select suitable participants.
( 3 marks)
h) Give one guideline that would help a student complete the observation of an
individual participant.
(3 marks)
4
A researcher uses a computer based image processing system to merge a set of passport
style photographs of young women to form a single, composite image. She suspects that
such composites are more likely to be judged as attractive. To investigate this possibility she
asks participants to rate the attractiveness of a set of 12 images and a composite. Participants
are simply asked to place the pictures in order of judged attractiveness and the order for each
picture is recoded.
a) If the composite image tends to be judged as average attractiveness what is its expected
rank?
(2 marks)
Sample values of the two tailed Chi
distribution
df 5% 1% 0.10%
1 3.84 6.63 10.83
2 5.99 9.21 13.82
3 7.81 11.34 16.27
b) A sample of 19 participants complete the ranking. The judged rank attractiveness of the
composite is shown in the table (more attractive is higher rank). Use the table to complete a
suitable test to assess the hypothesis.
Atractiveness Ranking
P No Composite Expected
1 11
2 10
3 9
4 8
5 8
6 11
7 6
8 9
9 12
10 7
11 12
12 10
13 10
14 9
15 11
16 12
17 7
18 3
19 13
a) How many Participants rank the composite precisely ‘as expected’?
(2 marks)
b) How many Participants give the composite a lower rank than that expected?
( 2 marks)
c) Complete the Wilcoxon Matched Pairs Signed Ranks Test on this data.
(10 marks)
d) What conclusion is supported by this analysis?
(3 marks)
Critical Values for Wilcoxon signed rank test
NB SMALLER OBSERVED VALUES are associated with
LOWER significance levels.
Probability for two tailed test:
N of pairs 0.10 0.05 0.02 0.01
13 21 17 13 10
15 30 25 20 16
17 41 35 28 23
19 53 46 38 32
e) Suggest an alternative statistical analysis that could have been used.
(2 marks)
f) Give details of one factor that is relevant to choosing the most appropriate test statistic.
(4 marks)
**End of test**

Did you manage to find the answers for all those questions. it would be a great help if i can have the answers as i can assess myself and practice on it..