Interpreting Confidence Intervals and p-values

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Im having difficulties understanding the connection between the p-values and CIs. Some of these results in the picture seem to be inconsistent. Starting with G1: divide the two sample means in order to acquire a t statistic which will then state that the difference between these two sample means represents the population mean. The H0 is: the difference between the two sample means is equal to 0 (there is no difference), with a p-value of 0.05. If the p-value is below 0.05 we reject the null hypothesis. If it's greater than 0.05 we fail to reject the hypothesis. So,
G1 has a p-value 0.02<0.05 --> we reject the null hypothesis We can't find a 0 in the confidence interval so we reject the null hypothesis. The population means are not equal. Fining a 0 in the interval would mean that we have found the H0 to be true. G2--> CI has a 0, p-value is 0.07>0.05 --> we fail to reject the H0. G3--> there is no 0 in CI --> we reject, and 0.09>0.05 we accept the H0 --Inconsistency! We would need to have a confidence interval including a 0. G4--> CI doesn't involve a 0 indicating there is a difference between the means--rejecting H0; 0.13 > 0.05 we accept the H0. Inconsistency! A better p-value would be more close to 0.05?

Thanks for bearing with me and having read the whole text! You can open the screenshot i "interpreted" here 2

1 Answers

I agree with your interpretations. In the case of G4, since the p-value is greater than 0.05 and the confidence interval is (23, 125), H0 cannot be a test that there is no difference between the means. Either that, or there is a typo somewhere.

Also, regarding:

A better p-value would be more close to 0.05?

Not really. This type of testing is binary. Either we accept reject the null hypothesis, or we fail to reject it. Obviously this leaves open problems such as a p-value of 0.049999 and 0.50001. Clearly these are essentially the same results, yet this kind of hypothesis testing would produce entirely different conclusions.

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