I got the wrong answer please help

A researcher intends to estimate the effect of a drug on the scores of human subjects perfolming a task of psychomotor coordination. The members of a random sample of 9 subjects were given the drug pn'or to testing. The mean score in this group was 9.23. and the sample variance was 17.79. An independent random sample of 10 subjects was used as a control group and given a placebo prior to testing. The mean score in this control group was 15.04. and the sample variance was 27.45. Assuming that the population distributions are normal with equal variances, nd a 90% condence interval for the difference between the population mean scores. The condence interval is 9.59 <: px p a: to two decimal places as needed x one or more of your responses is incorrect. lower limit correct but upper the formula for u condence interval estimate ofthe difference in means l5: and ll independent populations given below wherei i are _ e . samples sp _2 pooled sample vanance. n nx-iny n5r sizes tx critical value student t distn with nk degrees freedom an area ofuf2 tail>