State the hypotheses

Question

At Western University the historical mean of scholarship examination score for freshman applications is 900. Population standard deviation is assumed to be known as 180. Each year, the assistant dean uses a sample of applications to determine whether the mean examination score for the new freshman applications has changed.

a) State the hypotheses.

b) What is the 95% confidence interval estimate of the population mean examination score if a

sample of 100 applications provided a sample mean 935?

c) Use the confidence interval approach to conduct a hypothesis test. What is your conclusion?

d) Assuming α = .05, conduct p-value based and critical-value based hypothesis tests. How do the results compare in all the three cases?

 

Answer 1

(a)

Null Hypothesis H₀: µ =900

Alternative Hypothesis H₁: µ ≠ 900

(b)

C.I for mean = [X-bar - Z*SD/  < µ < X-bar + Z*SD/  ]

                       = [935 - 1.96*180/10 < µ < 935 + 1.96*180/10]

                       = [899.72, 970.28]

(c)

900 is just within the interval at lower end, so we can't reject null hypothesis.

(d)

Z-statistic = (935-900)/180/

                   = 1.94

1.94 is neither greater than 1.96 nor smaller than -1.96 so we can not reject null hypothesis. P-value will be slightly greater than level of significance α.