 |
 |
You can't draw this graph especially easily. The confidence interval that is relevant for a t-test is the confidence interval of the difference between the two means, not the confidence interval of each mean. However, for a t-test, I would wonder whether a graph is useful. You are only trying to show two numbers. You can show those two numbers in text, or in a table, and you can give the difference between them and the confidence interval, which is what you're interested in. I would write something like: Group 1 had a mean value of 17 (SD 4), group 2 had a mean of 19 (SD 3), thus group 2 had a mean which was 2 points higher (95% CIs 1, 3; p = 0.002). Jeremy On 21/04/2008, Mann, Helen N <[log in to unmask]> wrote: > > > > If you had done bar charts to show differences in mean scores for males and > females on 3 measures and you had indicated on your chart with a star where > the t-test had found significant sex differences (p<.001 and p<.05) but then > your supervisor said you need to show confidence intervals on your graphs > what would you do?!!? > > In the output from T-tests a 95% confidence interval is calculated...so > would you report that, if so how would you report it?!.....But surely, > shouldn't the person looking at the graph just assume that as you did a > t-test a 95% confidence interval level was taken into account so you don't > need to report it....?!?! > > Or would you scrap the bar chart altogether and just do an error bar graph?! > Or show both.... > > Any help would be most appreciated...(hope it all makes sense!) > > H* > (PS>> If there are any SPSS stats gurus in Edinburgh please contact me!) > ________________________________ > Heriot-Watt University is a Scottish charity registered under charity > number SC000278. > -- Jeremy Miles Learning statistics blog: www.jeremymiles.co.uk/learningstats Psychology Research Methods Wiki: www.researchmethodsinpsychology.com