Question

In 2011, a U.S. Census report determined that 71% of college students work. A researcher thinks this percentage has changed since then. A survey of 110 college students reported that 91 of them work. Is there evidence to support the reasearcher's claim at the 1% significance level? A normal probability plot indicates that the population is normally distributed.

Answer 1

Note: The full question is attached as picture below

a) Hо : p = 0.71

Ha : p ≠ 0.71

p = x / n

p = 91/110

p = 0.83.

1 - Pо = 1 - 0.71 = 0.29.

b) Test statistic = z

= p - Pо / [√Pо * (1 - Pо ) / n]

= 0.83 - 0.71 / [√(0.71 * 0.29) / 110]

= 0.12 / 0.043265

= 2.77360453

Test statistic = 2.77

c) P-value

P(z > 2.77) = 2 * [1 - P(z < 2.77)] = 2 * 0.0028

P-value = 0.0056

∝ = 0.01

P-value < ∝

Reject the null hypothesis. There is sufficient evidence to support the researchers claim at the 1% significance level.