Assume that the helium porosity (in percentage) of coal samples taken from any particular seam is normally distributed with true standard deviation 0.79. (a) compute a 95% ci for the true average porosity of a certain seam if the average porosity for 22 specimens from the seam was 4.85. (round your answers to two decimal places.)

Interval=4.85±0.33

Interval (5.18,4.52)

Step-by-step explanation:

Consider the formula for the interval:

interval=±

Where:

X is the mean value

S is the standard deviation

n is the sample size

Z is the distribution

Alpha=1-0.95=0.05

=1.96 (From Standard Z-Distribution Table)

Now use the above formula

interval=±

Interval=4.85±0.33

Interval (5.18,4.52)

c

step-by-step explanation:

8 2/3 is the answer

step-by-step explanation: just use a calculator