Question

The table shows the daily changes in the barometric pressure (in inches of mercury) for four days.

(a) What is the mean change?

(b) The mean change for Monday through Friday is $-0.01$ inch. What is the change in the barometric pressure on Friday? Explain.

Day	Change in Pressure
Monday	$-0.05$
Tuesday	$0.09$
Wednesday	$-0.04$
Thursday	$-0.08$

Answer 1

(a) Find the mean change:

Mean change $=\frac{sumofallobservations}{totalnumberofobservations}$

Mean change $=\frac{-0.05+0.09+(-0.04)+(-0.08)}{4}=\frac{-0.08}{4}$

Mean change $=-0.02$

(b) Find the change in the barometric pressure on Friday:

Mean change for Monday through Friday $=-0.01$ inch

Let change in pressure on Friday be $x$ inches

Mean change $=\frac{sumofallobservations}{totalnumberofobservations}$

$-0.01=\frac{-0.05+0.09+(-0.04)+(-0.08)+x}{5}$

On solving, $x=0.03$ inch

So, the change in barometric pressure on Friday $=0.03$ inch

Final Answer: (a) Mean change for Monday through Thursday $=-0.02$ inch

(b) The change in barometric pressure on Friday $=0.03$ inch