Use the given information to find the number of degrees of freedom, the critical values xi and XZR, and the confidence interval estimate of o. It is reasonable to assume that a simple random sample has been selected from a population with a normal distribution. Nicotine in menthol cigarettes 98% condence; n = 20, s = 0.24 mg. 3 Click the icon to View the table of Chi-Square critical values. (E df= E (Type a whole number.)