helpppp

Quote:

Originally Posted by bombo31

Fifty fifth-grade students from each of four city schools were given a standardized fifth-grade reading test. After grading, each student was rated as satisfactory or not satisfactory in reading ability, with the following results:

1 2 3 4 School

7 10 13 6 Not satisfactory

Is there sufficient evidence to indicate that the percentage of fifth-grade students with an unsatisfactory reading ability varies from school to school?

Null hypothesis is that there is no variation between schools. Then the
expected number not-satisfactory in each school would be 9.

Then the statistic:

$\chi^2=\sum \frac{(o_i-e_i)^2}{e_i}$

has a (approximatly) $\chi^2$ distribution with 3 degrees of freedom, where the
$o_i$ s are the observed frequencies and $e_i$ are the expected frequencies.

RonL