Statistics question
 

I've played 297 $30+3's and my sample mean return is $39.3 My standard deviation is $52.82. From this information I determined that my mean is 95% likely to be in between $33.29 and $45.31. My question is this: I know it is very unlikely that my ROI is above 25%, so my interval is probably really no higher than $41.25. How does affect my 95% confidence interval?