SOLUTION: A company that produces flashlight batteries wishes to know what percentage of its batteries will last longer than 30 hours. It selects and tests a random sample of 300 batteries.

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Question 726754: A company that produces flashlight batteries wishes to know what percentage of its batteries will last longer than 30 hours. It selects and tests a random sample of 300 batteries. Of these batteries, 225 last 30 hours or more.
Find the sample proportion. The sample proportion is _______. (Use 2 decimal place such as X.XX)
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
The sample size is 300. The number of successes are 225, so the sample proportion is

phat = x/n = 225/300 = 0.75

So the sample proportion is phat = 0.75

Notes:

1) phat (pronounced pee-hat) is the sample proportion that estimates the population proportion p. This is NOT the same as the p-value. The symbol you'll most likely see for phat is (basically a p with a ^ directly over it)

2) x = number of successes and n = sample size

3) A "success" in this case is finding a battery that lasts 30 hours or more. If you find a battery that lasts less than 30 hours, then it's not a success and it's a failure.

4) The sample proportion (phat) is equal to the ratio or fraction of the number of successes (x) over the number in the sample (n)