We are given that Thompson and Thompson is a steel bolts manufacturing company. Their current steel bolts have a mean diameter of 141 millimetres, and a standard deviation of 7.

A random sample of 39 steel bolts is selected.

Let $\bar X$ = sample mean diameter

The z score probability distribution for sample mean is given by;

Z = $\frac{ \bar X-\mu}{\frac{\sigma}{\sqrt{n} } } }$ ~ N(0,1)

where, $\mu$ = population mean diameter = 141 millimetres

$\sigma$ = standard deviation = 7 millimetres

n = sample of steel bolts = 39

Now, Percentage the sample mean would be greater than 141.4 millimetres is given by = P( $\bar X$ > 141.4 millimetres)

P( $\bar X$ > 141.4) = P( $\frac{ \bar X-\mu}{\frac{\sigma}{\sqrt{n} } } }$ > $\frac{141.4-141}{\frac{7}{\sqrt{39} } } }$ ) = P(Z > 0.36) = 1 - P(Z $\leq$ 0.36)

= 1 - 0.6406 = 0.3594

The above probability is calculated by looking at the value of x = 0.36 in the z table which has an area of 0.6406.

8 0

3 years ago

Please help thank you very much

-BARSIC- [3]

Hello!

The answer is 34°

Hope this helps!

7 0

3 years ago