Question

The gas mileage for a particular type of car is known to have a standard deviation σ = 1 mile. For a fixed speed (65 miles/hour) sixteen cars were tested and found to get an average of 24.3 miles per gallon. What is the z-test statistic for the null hypothesis H₀: μ = 25 miles per gallon?

a. -.7        b. -1.4          c.   -2.8        d. 1.4

If the z-test statistic for H₀: μ = 10 yields a p-value of .03. Should we reject H₀ at the 5% significance level? The 1% significance level?

a. Yes, No       b. No, Yes      c. Yes, Yes       d. No, No       

If 80% of the students in a course achieve scores greater than 80, but 20% get a 0 on the test, then which is most accurate and informative

a. the median is about 40. b. the median is greater than 80 and is greater than the mean   c. the mean is greater than the median   d. not enough information to tell.

When would you use a t-test rather than a z-test?

a. when you need to use the standard deviation of a small sample b. when the mean is very large   c. when you want the confidence interval to be narrower

Twenty-five weighings of a small object on a sensitive scale result in average of 8.23 grams. If the standard deviation σ of weighings on this scale is .15 grams, what is a 95% confidence interval for the true weight of the object?

a. 8.23 ±.02         b. 8.23 ±.04        c. 8.23 ±.06       d. 8.23 ±.08

Answer 1