PracticeMidterm2

# PracticeMidterm2 - MA 213 Fall 2007 Practice midterm 2...

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MA 213 Fall 2007 Professor: Michael J. Pencina Practice midterm 2 - Solutions 1. Double Multiple Choice: in the following questions exactly two answers are correct. If you give two correct answers you get 4 points; if you give only one answer and it is correct you get two points; if you give two answers, one correct and one incorrect, you get only 1 point; in all other situations you get zero points. 1.1 Which two are true: A) We are trying to prove, support or detect the null hypothesis; B) The level of significance is equal to the probability of the margin of error; C) The level of significance if equal to the probability of type I error; D) Type I error is committed if we reject the null if it is false; E) Type I error is committed if we reject the null if it is true; 1.2 We measured the pulse rate for each individual in a random sample of 23. Assume we have all the measurements. A) The 95% confidence interval (CI) for pulse rate would use a critical value of z=1.96; B) The 95% confidence interval (CI) for pulse rate would use a critical value of t=2.069; C) The 95% confidence interval (CI) for pulse rate would use a critical value of t=2.074; D) Since the population standard deviation is unknown we cannot construct a 95% CI for pulse rate; E) To construct the 95% CI we need to assume that pulse rate is approximately normal. 1.3 Let t1 and t2 be such numbers that P(t ≥ t1) = 0.025 and P(t ≤ t2) = 0.05. A) If degrees of freedom are 10 then t1 = 2.228; B) If degrees of freedom are 10 then t1 = - 2.228; C) If degrees of freedom are 13 then t2 = 1.771; D) If degrees of freedom are 13 then t2 = 1.761; E) t1 > t2 regardless of the degrees of freedom. 1.4 Assuming all other parameters are constant, in order to cut the margin of error in half we need to:

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PracticeMidterm2 - MA 213 Fall 2007 Practice midterm 2...

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