A manufacturer claims his light bulbs have a mean life of 1800 hours. A consumer

Question

A manufacturer claims his light bulbs have a mean life of 1800 hours. A consumer group tested a random sample of 250 bulbs and found them to have a sample mean life of 1790 hours and a sample standard deviation of 50 hours. Assess the manufacturer's claim.

i) What is the null hypothesis?

a) ? = 1800

b) x? = 1800

c) x? < 1800

d) ? > 1800

ii) What is the alternative hypothesis?

a) ? > 1800

b) x? < 1800

c) x? > 1800

d) ? < 1800

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

iv) What is the significance probability or P value. Choose the appropriate range.

a) P > .10

b) .05 < P ? . 10

c) .01 < P ? .05

d) P ? .01

v) Are the results statistically significant at the .05 level of significance? Yes or No?

Explanation / Answer

random sample of 250 bulbs and found them to have a sample mean life of 1790 hours and a sample standard deviation of 50 hours. Assess the manufacturer's claim.

i) What is the null hypothesis?

a) Mu = 1800

ii) What is the alternative hypothesis?

d) Mu < 1800

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

= -3.16

iv) What is the significance probability or P value. Choose the appropriate range.

d) P < .01

v) Are the results statistically significant at the .05 level of significance? Yes or No?

Yes.

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