1 test Truck pollution In an experiment to determine the eff

1 test

Truck pollution: In an experiment to determine the effect of ambient temperature on the emissions of oxides of nitrogen (NOx) of diesel trucks, 10 trucks were run at temperatures of 40 degree F and 80 degree F. The emissions, in parts per billion, are presented in the following table. Let mu 1 represent the mean emission at 10 degree F. Can you conclude that the mean emission differs between the two temperatures? Use the a = 0.1 level of significance and the U-81 calculator to answer the following.

Solution

The test hypothesis:

Ho: mu1=mu2 (i.e. null hypothesis)

Ha: mu1 not equal to mu2 (i.e. alternative hypothesis)

The test statistic is

t=(xbar1-xbar2)/sqrt(s1^2/n1+s2^2/n2)

=(835.52-802.93)/sqrt(61.873^2/10+40.444^2/10)

=1.39

It is a two-tailed test.

The degree of freedom =n1+n2-2=10+10-2=18

Given a=0.1, the critical values are t(0.05, df=18) =1.73 or -1.73 (from student t table)

The rejection regions are if t<-1.73 or t>1.73, we reject the null hypothesis.

Since t=1.39 is between -1.73 and 1.73, we do not reject the null hypothesis.

So we can not conclude that the mean emission differs between the two temperatures

40 F	80 F
835.520	802.930	mean
61.873	40.444	std. dev.
10	10	n