Recommended problems

1. problem We want to check whether the boxes has 90 tissues in them. Let us suppose, the the deviation is 4.5.

How many boxes have to be opened, to be sure on 95% confidence level, that there are 90 tissues in the box and not 89?

sampsizepwr('t',[90,4.5],89, 0.95)
% * And on 99% confidence level?
sampsizepwr('t',[90,4.5],89, 0.99)
% * Answers these two questions as a customer (we only care if there are
% less),
sampsizepwr('t',[90,4.5],89, 0.95,[],'Tail','left')

ans =

   266


ans =

   374


ans =

   221

sampsizepwr('t',[90,4.5],89, 0.99,[],'Tail','left')
% * and as a quality controller (every difference is a problem).

% we already got the answer in the first part.

ans =

   321

2. problem We want to test the effectiveness of a new antipyretic. We measured the temperatures of 10 people before taking the drug and got the following temperatures: 38.1, 39.2, 37.9, 38.3, 39.5, 39.4, 38.5, 39.1, 38.4, 39.1 Half an hour after taking the drugs: 37.3, 36.9, 37.3, 37.2, 38.2, 37.4, 36.5, 37.3, 37.4, 36.8. What is our null hypothesis? What is the alternative hypothesis? What sort of test we should apply?

before=[38.1, 39.2, 37.9, 38.3, 39.5, 39.4, 38.5, 39.1, 38.4, 39.1];
after=[37.3, 36.9, 37.3, 37.2, 38.2, 37.4, 36.5, 37.3, 37.4, 36.8];

Null hypothesis: the temperatures are the same, Alternative hypotheses: the temperature after taking the drug are lower. We apply two sample, one sided t-test.

ttest2(before, after,'Tail', 'right')

ans =

     1