H0: a 2 = 0 "2, and Hi" a 2 > 0 "2. From Table III, the critical X 2 value for ot - 0.05 with 15 dfis 25.00. Substituting in Eq. (19.1), we find X2 - df x s 2 15 x 1.2302

~ 2 -- 0.52 = 90.77.

Because the calculated X 2 is much larger than the critical value, we reject H0; the tympanic thermometer is too variable for clinical use. From a computer package, the p-value is zero to many decimal places; we would report p < 0.001.