Answer to Question #97265 in General Chemistry for kwabena

Question

Q5. The following data give the recovery of bromide from spiked samples of vegetable matter, measured by using a gas-liquid chromatographic method. The same method of bromide was added to each specimen.

Tomato: 777 790 759 790 770 758 764 g
Cucumber: 782 773 778 765 789 797 782 g

(a) Test whether the recoveries from the two vegetables have variances which differ significantly.
(b) Test whether the mean recovery rates differ significantly.

Answer 1

The null hypothesis adopted is that there is,

“there is no

difference in their reliability”.

•

Assuming that the workers use the laboratory for an

equal length of time, we would expect, from the null

hypothesis, the same number of breakages by each

worker.

•

Since the total number of breakages is 61, the expected

number of breakages per worker is 61/4 = 15.25.

It’s not possible in practice to have a non-integral

number of breakages.

•

The nearest practicable ‘equal’ distributions would be15,

15, 15, 16.

•

The question to be answered is whether the difference

between the observed and expected frequencies is so

large that the null hypothesis should be rejected.