Question

The laboratory experts its experiment this time testing 18 test tubes and finding it took reheating them an average of 1375 times until they cracked, with a standard deviation of 291. Compute the 95% confidence interval to estimate the mean number of times they can use the test tube. Does this support the test tube company's claim that the tubes can be used more than 1400 times before they crack?

Answer #1

Given that

mean = 1375

standard deviation = 291

sample size n = 18

degree of freedom = n-1= 18-1 = 17

t critical = 2.11 (using t distribution table with alpha = 0.05 and df =17)

Confidence interval =

it is clear that 1400 is included in the confidence interval and the upper limit of confidence interval is greater than 1400, so it is significantly more than 1400

therefore, it is supporting the test tube company's claim that the tubes can be used more than 1400 times before they crack

A laboratory is interested in how many times they can use a
specific brand of test tube on a Bunsen burner before it cracks.
Assume that the population is normally distributed. They test 20
test tubes and finding it took reheating them 1111 times until they
cracked, with a standard deviation of 234. Compute the 98%
confidence interval to estimate the average number of times they
can use the tube. You DO need to check CLT here

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new drug. Moreover, between 80 and 90 percent of drug candidates
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