In-class exercise 5: the one-sample tests of hypothesis

1. A light bulb manufacturer advertises that their bulbs have an average lifetime of at least 1000 hours. To verify this claim, a consumer testing agency randomly selects a sample of 36 bulbs, and finds that their average lifetime is 980 hours. It is known from prior testing that the population standard deviation is 60 hours.

1) Should we use a one-tailed or two-tailed test?

One-tailedTwo-tailed

2. 2) Compute the test statistic.

z = ______

3. 3) Determine the critical value(s) at α = 0.05.

Critical value(s) = ____________

4. 4) Determine the p-value.

p-value = ____________

5) Should we reject the null hypothesis?

Reject H₀Fail to reject H₀

2. A university is evaluating its claim that 80% of its graduates find a job within 6 months after graduation. To verify this, the career office surveys 120 recent graduates, and finds that 86 of them are currently employed.

1) Should we use a one-tailed or two-tailed test?

One-tailedTwo-tailed

7. 2) Compute the test statistic.

z = ______

8. 3) Determine the critical value(s) at α = 0.05.

Critical value(s) = ____________

9. 4) Determine the p-value.

p-value = ____________

5) Should we reject the null hypothesis?

Reject H₀Fail to reject H₀

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