I'm using ttest for two populations, I know that we can reject the null hypothesis when the p-value is less that 0.1 (with 90% confidence). but does it make sense to get a pvalue of say .17 and then say the two means are different with 83% confidence?
A p-value is used to assess the strength of the evidence against the Null hypothesis. A smaller p-value corresponds to stronger evidence against the Null hypothesis.
Let me clarify some details regarding Confidence: Confidence is not 1-p-value. Confidence is 1-Alpha, where alpha is a predetermined threshold to determine if a difference is significant.
Let's suppose we choose an Alpha = 0.05. If we perform the test and get a p-value=0.001, we can conclude: "There is sufficient evidence to reject the Null hypothesis". Confidence doesn't really mean anything when interpreting the results of the test, and it certainly does not mean that confidence is 1-0.001=0.999.
If you have a p-value of 0.17, this does not mean you have 83% confidence in the result. It simply means there is a 17% chance of obtaining the sample results assuming the Null hypothesis is true.
Confidence is less involved when discussing hypothesis testing, but more meaningful when discussing a confidence interval. Let me know if this helps answer your question. I'm happy to help further if needed.