TEST #1 – ECON 2202 – TUESDAY, JANUARY 26, 2010 – Professor Dubey
1. The test lasts 1 hour and 30 minutes It is worth 100 marks, and contains two sections:
a. Section A – 79 marks: 4 long-answer questions. Full explanations required. Use 5-step method
for hypothesis tests and confidence intervals. Round answers to at least 4 decimal places.
b. Section B – 20 marks: 5 short-answer questions. No explanations required, though they may earn
part-marks if your answer is incorrect or incomplete.
c. 1 bonus mark to start. If your solutions are not legible or tidy, you will lose this mark.
PART A –79 MARKS – LONG ANSWER QUESTIONS. For full marks, you must show your work,
including the formulae used, and use the 5-step method.
Q1. (18) A study is conducted on the amount of time teenagers spend on the internet, which is normally
distributed for both boys and girls. The population variances are unknown and unequal. Data from a
random sample of teenage girls and boys are summarized below.
Sample Results Boys (Population 1) Girls (Population 2)
Sample Size 16 9
Average Daily Internet Use (in hrs) 3.2 2
Standard Deviation (s) 4 1.5
You are also told (do not waste time verifying these calculations!):
232 and 20.9790
11
21
2
2
2
2
2
1
2
1
2
1
2
2
2
2
1
2
1
nn
n
ns
n
ns
n
s
n
s
a) (2) State (do not calculate) the formula to build a 95% confidence interval (CI) for the
difference in average daily Internet Use between boys and girls.
b) (2) Calculate the point estimate for the 95% CI.
c) (2) Determine the degrees of freedom for the 95% CI.
d) (2) Calculate the standard error in this question.
e) (10) Test the belief of Internet providers that boys and girls spent the same time on the internet,
on average, using a 5% significance level.
1
