drink tea for a stronger immune system we saw in exercise 6.245 on page 500 that drinking tea appears to offer a strong boost to the immune system. in a study extending the results of the study described in that exercise,60 blood samples were taken on five participants before and after one week of drinking about five cups of tea a day (the participants did not drink tea before the study started). the before and after blood samples were exposed to e. coli bacteria, and production of interferon gamma, a molecule that fights bacteria, viruses, and tumors, was measured. mean production went from 155 pg/ml before tea drinking to 448 pg/ml after tea drinking. the mean difference for the five subjects is 293 pg/ml with a standard deviation in the differences of 242. the paper implies that the use of the t-distribution is appropriate. why is it appropriate to use paired data in this analysis? find and interpret a 90% confidence interval for the mean increase in production of interferon gamma after drinking tea for one week.