Question

Under specified conditions, an automobile manufacturer is concerned about the miles per gallon (mpg) of its new compact car. For cars of the same class, the average is 23 with a standard deviation of 5 mpg. To investigate, the manufacturer tested 28 cars in which the average was 19 mpg. What can the car manufacturer conclude with α = 0.05?

a) Compute the corresponding effect size(s) and indicate magnitude(s).
If not appropriate, input and select "na" below.
d =     ______ ; Select--- na, trivial effect, small effect, medium effect, large effect
r² = _______ ;Select--- na, trivial effect, small effect, medium effect, large effect

b) Make an interpretation based on the results.

a. Under specified driving conditions, the new compact car gets significantly more mpg than cars in its class.

b. Under specified driving conditions, the new compact car gets significantly less mpg than cars in its class.     

c. Under specified driving conditions, the new compact car does not get significantly different mpg than cars in its class.

Answer 1

Ans:

a)

Cohen's d=(19-23)/5=0.80,large effect

r^2 is na

b)

Under specified driving conditions, the new compact car gets significantly less mpg than cars in its class.