Question

STATISTICS – HELP! Hypothesis Testing: ‘There is no difference between the products’ effectiveness’.

1)Using the variable Score A – Score B, conduct a two-tailed Z-test at the 5% significance level to determine if there is really a statistically significant difference between the effectiveness of each mouthwash. Check that the conditions are met to use the z-test.

2) Calculate the 95% confidence interval for the difference between the scores.

Answer 1

I'm having trouble with the confidence interval part...not sure which proportion to use... see table below, regarding
"Eight of the volunteers were given mouthwash A first and then mouthwash B second. The other eight volunteers were given mouthwash B first and then mouthwash A second."

Answer 2

\[p^*-1.96\sqrt{\frac{ p^*(1-p^*) }{ n }} \le p \le p^*+1.96\sqrt{\frac{ p^*(1-p^*) }{ n }}\]

Answer 3

I know this formula, but im not sure what p* should be...

Answer 4

any ideas?

Answer 5

the null hypothesis is that the mean of Score A - Score B is zero

Answer 6

and you need to do a paired data test

Answer 7

the tricky part of the problem is that they change the order of the mouthwash

Answer 8

Is this a two sampZInt?

Answer 9

Well, it doesn't look like there are any proportions in this problem, it's just values. So you'd use the formula for that instead.

Answer 10

@BarbaraKara
Can you post the entire question with all the english. there seems to be something missing

Answer 11

the samples are not independent samples, since it is the same person trying the two different mouthwashs

Answer 12

I mean each subject tries two different mouthwash

Answer 13

so i would do a 2 sample T test pooled or paired data.