Assume we have an observed sample proportion of 40 a null v

Assume we have an observed sample proportion of .40 , a null value of .35, (we are testing to see if the proportion of all adults who prefer blue cars has changed from .35 since industry statistics indicate the this proportion was .35 in the past), and an SE under the null hypothesis of 0.015 . What is our test statistic value (standardized score)?

A) +6.66
B) -6.66
C) -3.33
D) +3.33

Solution

As

z = (p^ - p0)/SE

Then as p^ = 0.40 (Sample proportion), p0 = 0.35 (null value), and SE = 0.015,

z = (0.40-0.35)/0.015 = 3.33 [ANSWER, D]