A manufacturer claims his light bulbs have a mean life of 1900 hours. A consumer

Question

A manufacturer claims his light bulbs have a mean life of 1900 hours. A consumer group tested a random sample of 260 bulbs and found them to have a sample mean life of 1890 hours and a sample standard deviation of 50 hours. Assess the manufacturer's claim.

a) What is the null hypothesis?
1. = 1900
2.x = 1900
3.x < 1900
4. > 1900

b) What is the alternative hypothesis?
1. > 1900
2.x < 1900
3.x > 1900
4. < 1900

c) Give the value of the test statistic, to two places past the decimal point.

d) What is the significance probability or P value. Choose the appropriate range.
1.P > .10
2. .05 < P . 10
3. .01 < P .05
4.P .01

e) Are the results statistically significant at the .05 level of significance?
1.Yes
2.No

Explanation / Answer

Null hypothesis is = 1900

ALternative hypothesis is < 1900

C) Test stastic is (x- )/(sigma/sqrt(n)) = (1890-1900)/[50/sqrt(260)]= -3.223

D) P-value for z = -3.223 is 0.000634. Hence,D

E) The result is significant at p < 0.05.

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