# Statistics

• Nov 22nd 2008, 08:13 AM
gibonwa33
Statistics
A large oil company recently conducted a survey amongst motorists to find out their preference among five leading brands of petrol:

Brand preferred...Number of motorists
Caltex ......................118
BP .............................92
Shell ........................135
Trek ..........................88
Engen ......................102

Test the hypothesis that the preference is uniform over the five brands of fuel at the 0.01 level of significance. (Angry)
• Nov 22nd 2008, 10:04 AM
CaptainBlack
Quote:

Originally Posted by gibonwa33
A large oil company recently conducted a survey amongst motorists to find out their preference among five leading brands of petrol:

Brand preferred...Number of motorists
Caltex ......................118
BP .............................92
Shell ........................135
Trek ..........................88
Engen ......................102

Test the hypothesis that the preference is uniform over the five brands of fuel at the 0.01 level of significance. (Angry)

You will be doing a $\chi ^2$ test goodness of fit test. The null hypothesis is that there is no difference in preference, and so as the total number of observations is 535, the expected frequencies for each brand are all 107.

So We have a table:

Code:

O(bserved)  E(xpected) 118          107  92          107 135          107  88          107 102          107
Then:

$
\chi^2=\sum_{i=1}^5 \frac{(O_i-E_i)^2}{E_i}
$

and we have 4 degrees of freedom.

You will need to look up the p-value for the value of $\chi^2$ in a table to complete the test.

CB