HW5 Grading Key (Biostat) Assigned 10/11; due 10/18. Grading sample is 5.2, 5.4, 5.10, and 5.12. Each problem is worth 2.5 points.

5.2 Parameter or estimate? (A) Estimate (B) Parameter, estimate (C) All are statistical estimates.
5.3 Serum cholesterol in undergraduate men. See key for odd-numbered problems.

5.4 Lab measurements 
(A) The standard deviation of the x-bars (i.e., the SEM) = 10 / 4 = 5
(B) n = (10 / 2)2 = 25 
(C) The average of several measurements is a more likely to be close to true mean � than is an individual measurement. 

5.5 Sampling behavior of means based on n = 30 from X~N(55.5, 4). See key for odd-numbered problems

5.6 Test scores
(A) The sampling distribution of x-bar has a standard deviation (SEM) of 50 / 100 = 5
(B) x-bar ~ N(250, 5) in picture form [graph not rendered on the web]
(C) Shade the region between 240 and 260.
(D) 240 ... 250
5.7  A survey of health problems. Done in lab; also see see key for odd-numbered problems.
5.9 Pharmacy survey. See see key for odd-numbered problems

5.10 Misinterpreting confidence intervals. The pharmacist is incorrect. The confidence interval applies to the probable location of population mean �. It does not apply to the distribution of values for the variable "cost of the drug." 

5.11 95% confidence interval for �. See see key for odd-numbered problems.

5.12  Muscle strength scores.
SEM = 12 / 15 = 3.098
95% confidence interval for � = x-bar � (1.96)(SEM) = 84.3 � (1.96)(3.098) =  84.3 � (1.96)(3.098) = 84.3 � 6.1 = (78.2, 90.4) 
Interpretation: We are 95% confident that population mean � is between 78.2 and 90.4. 
5.13 95% confidence interval for �. See see key for odd numbered problems.