Question

Lisa wants to determine if graduates from her college earn different incomes compared to graduates from college in general. To test this, Lisa sends surveys to 1,000 graduates from her school and finds that the average income is $40,000 ( s = 5,000). If the average income is $45,000 for graduates in general, do graduates from Lisa's school differ significantly? Report the results in APA style and be sure to include information about effect size.

Answer 1

Claim : Average income is different than $45000

H0 : µ = 45000 vs Ha : µ ≠ 45000

Given : = 40000 , s = 5000 , n = 1000

Since sample size is large we use z statistic.

Test statistic:

Z = =

Z = -31.62

P-value = P( z < -31.62 ) = 0 ---( from z score table )

2*P( z < -31.62 ) = 0

P- value = 0

Decision: As P value is less than α = 0.05 , we reject H0

Conclusion: There is significant evidence that average income is different than $45000

Effect size ( d ) =

Effect size ( d ) = 1

APA format :

A one sample z-test for means was conducted comparing the average income of graduate students differnet than µ = 45000 ( =40000 , S= 5000 ) . The result was statistically significant (z = -31.62, P- value = 0.05, two-tailed ).The magnitude of this effect, however, was very large ( d = 1 )