An article about driving practices in Strathcona County, Alberta claimed that 48% of drivers did not stop at stop sign intersections on county roads (Edmonton Journal, July 19, 2000). Two months later a follow-up study collected data in order to see whether this percentage had changed. The follow-up study found 360 of 800 drivers did not stop at stop sign intersections. Has there been a change in the proportion of drivers who do not stop. Test at the .05 significance level.
Opinion Research International surveyed people whose household incomes exceeded $50,000 and asked each for their top money-related new year's resolutions. The responses were:
Response Number of Respondents
1. Get out of credit card debt 115
2. Retire before age 65 50
3. Die broke 37
4. Make do with current finances 176
5. Look for a higher-paying job 50
Estimate with 90% confidence the proportion of people whose income exceeded $50,000 whose top money-related resolution is to look for a higher-paying job.
3) Suppose the prime minister wants an estimate of the proportion of the population who support the March, 2012 budget. The prime minister wants the estimate to be within 0.05 of the true proportion. Assume a 95% level of confidence. The prime minister's political advisors estimated the proportion supporting the current policy to be 0.45.
a) How large a sample is required?
b) How large a sample would be necessary if no estimate were available for the proportion that support current policy?
4) A sales manager collected the following data on annual sales and years of experience.
Salesperson Years of Experience Annual Sales (thousand $)
1 1 80
2 3 97
3 4 92
4 4 102
5 6 103
6 8 111
7 10 119
8 10 123
9 1 117
10 13 136
a) Draw a scatter diagram.
b) Determine the coefficient of correlation.
c) Interpret this measure.
d) Calculate the coefficient of determination.
e) What does this measure tell you?
f) Using 5% level of significance, can we conclude that there is a linear relationship between the two variables?
g) If we want to estimate annual sales based on years of experience, which variable is the dependent variable and which is the independent variable?
h) Determine the regression equation.
i) Interpret b(the slope).
j) Estimate the annual sales for a salesperson with 9 years of experience.