Question

A student measured the lead content of a paint sample 4 times. The standard deviation of the measurements was found to be 0.76% of the average. Calculate the confidence interval at the 90% confidence level.

Answer 1

`CI =0.894%`

Explanation:

From the question we are told that:

Sample size
`n=4`

Standard deviation
`\sigma=0.76\% of \=x`

Confidence level
`\mu =90\%=0.90`

Degree of Freedom
`Df=n-1=3`

Therefore

Test T from table is given

`t=2.353`

Generally the equation for Confidence interval CI is mathematically given by

`CI =t*(\sigma)/(√(n))`

`CI =2.353*(0.76)/(√(4))`

`CI =0.894%`