Question

In monitoring lead in the air after the explosion at the battery factory, it is found that the amounts of lead over a 6 day period had a standard error of 1.93. Find the margin of error that corresponds to a 95% confidence interval. (Round to 2 decimal places)

Answer 1

The margin of error that corresponds to a 95% confidence interval is 4.96.

Explanation:

We have the standard error(which is the same as the standard deviation of the sample), so we use the students t-distribution to solve this question.

The first step to solve this problem is finding how many degrees of freedom, we have. This is the sample size subtracted by 1. There are 6 days, so

df = 6 - 1 = 5

95% confidence interval

Now, we have to find a value of T, which is found looking at the t table, with 35 degrees of freedom(y-axis) and a confidence level of
`1 - (1 - 0.95)/(2) = 0.975([tex]t_(0.975)`). So we have T = 2.5706

The margin of error is:

M = T*s = 2.5706*1.93 = 4.96

The margin of error that corresponds to a 95% confidence interval is 4.96.