The manufacturer of a certain type of new cell phone battery claims that the average life span of the batteries is 500 charges;
that is, the battery can be charged at least 500 times before failing. To investigate the claim, a consumer group will select a random sample of cell phones with the new battery and use the phones through 500 charges of the battery.a. If the claim is true, what is P( X ≤ 36.7) ?b. Based on the answer to part (a), if the claim is true, is a sample mean lifetime of 36.7 hours unusually short?c. If the sample mean lifetime of the 100 batteries were 36.7 hours, would you find the manufacturer's claim to be plausible? Explain.d. If the claim is true, what is P( X ≤ 39.8)?e. Based on the answer to part (d), if the claim is true, is a sample mean lifetime of 39.8 hours unusually short?f. If the sample mean lifetime of the 100 batteries were 39.8 hours, would you find the manufacturer's claim to be plausible? Explain.
1 answer:
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Answer:
And the confidence interval for the difference is between:
Step-by-step explanation:
We have the following info given:
sample mean for medium Pizzas from Prim's
sample mean for medium Pizzas from Pizza Place
sample deviation for Prim's
sample deviation for Pizza Palca
sample size selected for each case
The confidence interval for the difference of means is given by:
And for the 95% confidence we need a significance level of and
, the degrees of freedom are given by:
And the critical value would be
And replacing we got:
And the confidence interval for the difference is between: