48. A Statistics 1si/1P1 term test had 50 multiple-choice questions, each with four possible answers, only one of which was correct. Suppose that one of the students who wrote the test answered each of the questions with an independent random guess. Determine an approximate probability that they answered at least 20 questions correctly if they could eliminate two wrong answers for each question and randomly chosen among the remaining answers? (a) 0.9406. (b) 0.5881. (c) 0.1077. (d) 0.0594.

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48. A Statistics 181/1P1 term test had 50 multiple-choice questions, each with four possible answers, only one of
which was correct. Suppose that one of the students who wrote the test answered each of the questions with
an independent random guess. Determine an approximate probability that they answered at least 20 questions
correctly if they could eliminate two wrong answers for each question and randomly chosen among the remaining
answers?
(a) 0.9406.
(b) 0.5881.
(c) 0.1077.
(d) 0.0594.
49. The administrators for a hospital wished to estimate the average number of days required for treatment of patients
between the ages of 22 and 33. A random sample of 800 hospital patients between these ages produced a mean
and standard deviation equal to 6.1 and 2.2 days, respectively. A 98% CI is given by [5.9191; 6.2808]. Interpret
this interval.
(a) The true average number of days required for treatment of patients between the ages of 22 and 33 is in this
interval with 98% confidence.
(b) With a repeated random sampling of size 800, the true average number of days required for treatment of
patients between the ages of 22 and 33 will be in this interval 98% of the time.
(c) The sample mean = 6.1 is in this interval 98% of the time.
(d) The true average number of days required for treatment of patients between the ages of 22 and 33 is in this
interval with a probability of 98%.
(Questions 50-52] A new drug is proposed to lower total cholesterol and a study is designed to evaluate its efficacy. Fifteen
patients were randomly selected to participate in the study and each is asked to take the new drug for 6 weeks. Before
starting the treatment, each patient's total cholesterol level is measured. The initial measurement is a pre-treatment or
baseline value. After taking the drug for 6 weeks, each patient's total cholesterol level is measured again and the differences
between the values for subject (Baseline – 6 Weeks) are shown below.
You may assume normality.
Subject 1| 2 | 3| 4| 5| 6|7| 8 |9| 10 | 11 | 12 | 13 | 14 | 15
d.
|10 34 40 30 13 13 13 20 6 13|-12| -2| 367
50. Which is the correct set of hypotheses for this study?
(a) Ho : Ha = 0 vs H1 : Ha < 0.
(b) Ho : 41 - µ2 = 0 vs H1 : H - #2 < 0.
(c) Ho : H4 = 0 vs H1 : 44 >0.
(d) Ho : d = 0 vs Hi :d< 0.
51. Which is the correct rejection region at the 5% level of significance?
(a) Taba> t13.0.025 = 2.160.
(b) Tobs > t14.00.05 = 1.761.
(c) Tubel >t40.025 = 2.145.
(d) Tobe > t1a0.05 = 1.771.
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STA 1s1/1P1: September 2021
page 15 of 21
52. If the following table represents the Statistica output for this study
T-test for Dependent Samples
Std.Dev
Mean
Diff
Std.Dev
t
p- value
Conf.
Conf.
Variable
Diff
-95%
+95%
Baseline
204.7
12.67
6-Weeks
191.8
12.59
12.93
13.63
3.675
0.0025
5.3852
20.4815
Which statement is true?
(a) Since the 95% confidence interval is ( 5.3852 , 20.4815 ) we can conclude there is no difference in the
cholesterol levels between the baseline and the 6-weeks.
(b) The 6-weeks cholesterol levels are in general higher than the baseline levels.
(c) Since p - value = 0.0025 < a, we can conclude that the mean difference between the baseline and 6-weeks
cholesterol levels is insignificant.
(d) Since the 95% confidence interval is ( 5.3852 , 20.4815 ) we can conclude there is a difference in the
cholesterol levels between the baseline and the 6-weeks.
53. Which of the following statements are true regarding the shape of distributions for quantitative
data?
(a) When the mean, median and mode are equal then the data is skewed.
(b) When the mean, median and mode are equal then the data is symmetrical.
(c) When the mean is less than the mode then the data is positively skewed.
(d) The shapes of distributions are determined by the mode only.
Transcribed Image Text:48. A Statistics 181/1P1 term test had 50 multiple-choice questions, each with four possible answers, only one of which was correct. Suppose that one of the students who wrote the test answered each of the questions with an independent random guess. Determine an approximate probability that they answered at least 20 questions correctly if they could eliminate two wrong answers for each question and randomly chosen among the remaining answers? (a) 0.9406. (b) 0.5881. (c) 0.1077. (d) 0.0594. 49. The administrators for a hospital wished to estimate the average number of days required for treatment of patients between the ages of 22 and 33. A random sample of 800 hospital patients between these ages produced a mean and standard deviation equal to 6.1 and 2.2 days, respectively. A 98% CI is given by [5.9191; 6.2808]. Interpret this interval. (a) The true average number of days required for treatment of patients between the ages of 22 and 33 is in this interval with 98% confidence. (b) With a repeated random sampling of size 800, the true average number of days required for treatment of patients between the ages of 22 and 33 will be in this interval 98% of the time. (c) The sample mean = 6.1 is in this interval 98% of the time. (d) The true average number of days required for treatment of patients between the ages of 22 and 33 is in this interval with a probability of 98%. (Questions 50-52] A new drug is proposed to lower total cholesterol and a study is designed to evaluate its efficacy. Fifteen patients were randomly selected to participate in the study and each is asked to take the new drug for 6 weeks. Before starting the treatment, each patient's total cholesterol level is measured. The initial measurement is a pre-treatment or baseline value. After taking the drug for 6 weeks, each patient's total cholesterol level is measured again and the differences between the values for subject (Baseline – 6 Weeks) are shown below. You may assume normality. Subject 1| 2 | 3| 4| 5| 6|7| 8 |9| 10 | 11 | 12 | 13 | 14 | 15 d. |10 34 40 30 13 13 13 20 6 13|-12| -2| 367 50. Which is the correct set of hypotheses for this study? (a) Ho : Ha = 0 vs H1 : Ha < 0. (b) Ho : 41 - µ2 = 0 vs H1 : H - #2 < 0. (c) Ho : H4 = 0 vs H1 : 44 >0. (d) Ho : d = 0 vs Hi :d< 0. 51. Which is the correct rejection region at the 5% level of significance? (a) Taba> t13.0.025 = 2.160. (b) Tobs > t14.00.05 = 1.761. (c) Tubel >t40.025 = 2.145. (d) Tobe > t1a0.05 = 1.771. page 14 of 21 Page Tatal: Version 40 STA 1s1/1P1: September 2021 page 15 of 21 52. If the following table represents the Statistica output for this study T-test for Dependent Samples Std.Dev Mean Diff Std.Dev t p- value Conf. Conf. Variable Diff -95% +95% Baseline 204.7 12.67 6-Weeks 191.8 12.59 12.93 13.63 3.675 0.0025 5.3852 20.4815 Which statement is true? (a) Since the 95% confidence interval is ( 5.3852 , 20.4815 ) we can conclude there is no difference in the cholesterol levels between the baseline and the 6-weeks. (b) The 6-weeks cholesterol levels are in general higher than the baseline levels. (c) Since p - value = 0.0025 < a, we can conclude that the mean difference between the baseline and 6-weeks cholesterol levels is insignificant. (d) Since the 95% confidence interval is ( 5.3852 , 20.4815 ) we can conclude there is a difference in the cholesterol levels between the baseline and the 6-weeks. 53. Which of the following statements are true regarding the shape of distributions for quantitative data? (a) When the mean, median and mode are equal then the data is skewed. (b) When the mean, median and mode are equal then the data is symmetrical. (c) When the mean is less than the mode then the data is positively skewed. (d) The shapes of distributions are determined by the mode only.
54. The probability is p = 0.40 that a patient with a certain disease will be unsuccessfully treated with a new medical
treatment. Suppose that the expected value of the number of patients who are successfully treated is 39. How
many patients was the treatment used on?
(a) 65.
(b) 97.5.
(c) 15.6.
(d) 98.
55. For the hypotheses Ho : p = 0.2 vs H1 : p > 0.2, with an n = 100 and p = 0.24, what is the numerical value of the
observed value of the test statistic, that is the numerical value of Zob,?
(a) 0.04.
(b) 0.24.
(с) 1.
(d) 0.2.
56. Suppose we are considering two populations with s = 4.43 and s2 = 5.93. Assume that the population variances
are equal and that n = ng. The pooled sample standard deviation is given by:
(a) 5.18.
(b) It cannot be determined because the sample sizes from each population must be specified.
(c) 27.3949.
(d) 5.2340.
page 15 of 21
Page Total:
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STA 1s1/1P1: September 2021
page 16 of 2
57. If the critical value of a lower tailed test is z = -1.645, which is the correct numerical value of the confidence
level?
(a) 95%.
(b) 97.5%.
(c) 5%.
(d) 90%.
58. Suppose you wish to construct a 99% confidence interval for the mean when the population variance is unknown.
You have a sample size of n = 300 and you make use of the t-table to determine the critical value. You go ahead
and look up under degrees of freedom oo and probability 0.005 and find the critical value to be 2.576. Your friend in
class used the inverse normal table instead, under the area 0.995 and found the same answer as you for the critical
value. Was this just a coincidence or is there theory involved to explain why this is the case?
(a) It was just a coincidence, there is no theory that exists to explain why the answers matched.
(b) The answers were the same because there is no difference between the t-distribution and the normal distri-
bution, the one implies the other.
(c) The answers were the same because the t-distribution approximates the normal distribution for large sample
sizes.
(d) The answers were the same because the t-distribution and the normal distribution are both symmetrical
distributions.
59. Achievement scores for a university entrance examination are normally distributed with a standard devia-
tion of 1.314. If 97% of the scores are between 56.6083 and 62.3111, what is the mean for this distribu-
tion?
(a) 53.7569.
(b) 59.4597.
(e) -59.4597.
(d) 58.5644.
60. Suppose a random sample ofn pupils at Greenpoint Secondary School located in the Eastern Cape, were asked
if they were in favour of having a one day on and one day off schedule for classes during the Covid 19 pandemic.
A proportion of 75%, which translates to 375 pupils who were in favour of having a one day on and one day off
schedule for classes during the Covid 19 pandemic. What was the sample size? At a 95% level of confidence, the
error margin is:
(a) n = 500 and the error margin is 0.0380.
(b) n = 375 and the error margin is 0.0438.
(c) n = 500 and the error margin is 0.0319.
(d) n = 375 and the error margin is 0.0224.
61. Nearly a quarter of current South African university undergraduates are confident that doing an internship will
help give them skills or knowledge to succeed in the job market and the workplace. This was the conclusion that
was reached after a survey of 90 000 students at 26 randomly selected institutions in South Africa. Which of the
following is false?
(a) Approximately a quarter is a statistic that was determined by the survey.
(b) Approximately a quarter is a parameter that was determined by the survey.
(c) The sample was the 90000 students who were surveyed.
(d) The population was all undergraduate South African students at the various institutions.
Transcribed Image Text:54. The probability is p = 0.40 that a patient with a certain disease will be unsuccessfully treated with a new medical treatment. Suppose that the expected value of the number of patients who are successfully treated is 39. How many patients was the treatment used on? (a) 65. (b) 97.5. (c) 15.6. (d) 98. 55. For the hypotheses Ho : p = 0.2 vs H1 : p > 0.2, with an n = 100 and p = 0.24, what is the numerical value of the observed value of the test statistic, that is the numerical value of Zob,? (a) 0.04. (b) 0.24. (с) 1. (d) 0.2. 56. Suppose we are considering two populations with s = 4.43 and s2 = 5.93. Assume that the population variances are equal and that n = ng. The pooled sample standard deviation is given by: (a) 5.18. (b) It cannot be determined because the sample sizes from each population must be specified. (c) 27.3949. (d) 5.2340. page 15 of 21 Page Total: Version 40 STA 1s1/1P1: September 2021 page 16 of 2 57. If the critical value of a lower tailed test is z = -1.645, which is the correct numerical value of the confidence level? (a) 95%. (b) 97.5%. (c) 5%. (d) 90%. 58. Suppose you wish to construct a 99% confidence interval for the mean when the population variance is unknown. You have a sample size of n = 300 and you make use of the t-table to determine the critical value. You go ahead and look up under degrees of freedom oo and probability 0.005 and find the critical value to be 2.576. Your friend in class used the inverse normal table instead, under the area 0.995 and found the same answer as you for the critical value. Was this just a coincidence or is there theory involved to explain why this is the case? (a) It was just a coincidence, there is no theory that exists to explain why the answers matched. (b) The answers were the same because there is no difference between the t-distribution and the normal distri- bution, the one implies the other. (c) The answers were the same because the t-distribution approximates the normal distribution for large sample sizes. (d) The answers were the same because the t-distribution and the normal distribution are both symmetrical distributions. 59. Achievement scores for a university entrance examination are normally distributed with a standard devia- tion of 1.314. If 97% of the scores are between 56.6083 and 62.3111, what is the mean for this distribu- tion? (a) 53.7569. (b) 59.4597. (e) -59.4597. (d) 58.5644. 60. Suppose a random sample ofn pupils at Greenpoint Secondary School located in the Eastern Cape, were asked if they were in favour of having a one day on and one day off schedule for classes during the Covid 19 pandemic. A proportion of 75%, which translates to 375 pupils who were in favour of having a one day on and one day off schedule for classes during the Covid 19 pandemic. What was the sample size? At a 95% level of confidence, the error margin is: (a) n = 500 and the error margin is 0.0380. (b) n = 375 and the error margin is 0.0438. (c) n = 500 and the error margin is 0.0319. (d) n = 375 and the error margin is 0.0224. 61. Nearly a quarter of current South African university undergraduates are confident that doing an internship will help give them skills or knowledge to succeed in the job market and the workplace. This was the conclusion that was reached after a survey of 90 000 students at 26 randomly selected institutions in South Africa. Which of the following is false? (a) Approximately a quarter is a statistic that was determined by the survey. (b) Approximately a quarter is a parameter that was determined by the survey. (c) The sample was the 90000 students who were surveyed. (d) The population was all undergraduate South African students at the various institutions.
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