Question

Nine owners of Honda Civics in Richmond want to know if they get different gas mileage with their cars than what the Honda Corporation reports. Honda of America states that all Honda Civics sold in America get an average of 33 MPG (miles per gallon). The nine Honda owners drive their cars and record the MPG listed below. Use a single-sample t-test to determine the outcome (alpha = .05, two-tailed).

Owner 1: 29 MPG
Owner 2: 32 MPG
Owner 3: 31 MPG
Owner 4: 30 MPG
Owner 5: 30 MPG
Owner 6: 29 MPG
Owner 7: 28 MPG
Owner 8: 31 MPG
Owner 9: 30 MPG
M = 30

In the box below, provide the following information:
Null Hypothesis in sentence form (1 point):
Alternative Hypothesis in sentence form (1 point):
Critical Value(s) (2 points):
Calculations WITH COHEN'S D (4 points): Note: the more detail you provide, the more partial credit that I can give you if you make a mistake.
Outcome (determination of significance or not, and what this reflects in everyday language, 2 points)

Answer 1

(a) Null Hypothesis in sentence form :

H0: Null Hypothesis: = 33 ( Gas mileage with their cars of Nine owners of Honda Civics in Richmond are same as what the Honda Corporation reports)

(b) Alternative Hypothesis in sentence form :

H0: Null Hypothesis: 33 ( Gas mileage with their cars of Nine owners of Honda Civics in Richmond are different from what the Honda Corporation reports)

(c)

= 0.05

ndf = n - 1 = 9 - 1 = 8

From Table, critical values of t = 2.3060

(d)

From the given data, the following statistics are calculated:

n = 9

= 270/9 = 30

s = 1.2247

SE = s/

= 1.2247/

= 0.4082

Test Statistic is given by:

t = (30 - 33)/0.4082

= - 7.3487

Since calculated value of t = - 7.3487 is less than critical value of t = - 2.3060, the difference is significant. Reject null hypothesis.

Conclusion:

The data support the claim that gas mileage with their cars of Nine owners of Honda Civics in Richmond are different from what the Honda Corporation reports.

Cohen's D is got as follows:

Since Cohen's d = 2.4496 > 0.8 we conclude that the Effect Size is Large.

(e)

Outcome:

the difference is significant. The data support the claim that gas mileage with their cars of Nine owners of Honda Civics in Richmond are different from what the Honda Corporation reports.