Statistic Task!

Joha

New Member
#1
A newspaper reports that teenagers on average talk 4 times on the phone per night. The headmaster of the school believes that this is too high. He samples 25 teenagers and gets an average of 3.4 calls per night with a standard deviation of 0.9 calls. I want to test this at a 99% confidence level (α = 0.01) and have answered the following. Is it correct? If not, what have I done wrong?
H0: µ ≤ 4
Ha: µ > 4
n = 25
degrees of freedom = 24
α = 1- c = 1 – 0,99 = 0,01
Zc = 2,33
Z = (x̄ -μ)/(s/√n) = (3,4-4)/(0,9/√25) = -3,33
Conclusion: Z = -3.33 <Zc = 2.33 --> we cannot reject the null hypothesis that teens talk on average 4 times on the phone every night.