Question

Considered safe for agricultural use. A well in Texas is used to water crops. This well is tested on a regular basis for arsenic. A random sample of 36 tests gave a sample mean of = 7.3 ppb arsenic, with s = 1.9 ppb. Does this information indicate that the mean level of arsenic in this well is less than 8 ppb? Use a 0.01 level of signifcance..

Answer 1

This information indicates that the mean level of arsenic in this well is less than 8 ppbat 0.01 level of signifcance..

Explanation:

Given that a well in Texas is used to water crops.

This well is tested on a regular basis for arsenic.

A random sample of 36 tests gave a sample mean of = 7.3 ppb arsenic, with s = 1.9 ppb

H0: Sample mean = 8

Ha: Sample mean <8

(left tailed test at 1% level)

Mean difference =-0.70

Std error of mean =
`(1.9)/(√(36) ) \\=0.3167`

Test statistic t = -2.204

df = 35

p value = 0.0171

Since p >0.01 we accept H0

This information indicates that the mean level of arsenic in this well is less than 8 ppbat 0.01 level of signifcance..