Question

A doctor wants to estimate the mean HDL cholesterol of all 20- to 29-year-old females. How many subjects are confidence affect the sample size required? Click the icon to view a partial table of critical values. A 99% confidence level requires subjects. (Round up to the nearest subject) A 90% confidence level requires subjects. (Round up to the nearest subject.) How does the decrease in confidence affect the sample size required? O A. Decreasing the confidence level decreases the sample size needed OB. The sample size is the same for all levels of confidence, O c. Decreasing the confidence level increases the sample size needed

Answer 1

errol Margin of er s (standard deviation) where Za critical value mn sumple size confidence > x = 0.01 2.576 0 ) So, gog A = 1.645 X 19.4 4. 19.4 We know that, Margin of error = Zala - I h When level is 99% - = 20.005 ( Source - STATKEY Cimage attached) 4 = 2.576 X 19.4 vn n = 156.09 ::A.994. confidence level requires 156 subjects. When confidence level is 90.). 2-0.10 Zal = 20-05 = 1-645 (source- STATKEY Cimage attached) vn on calculating , n = 63.65 ~ A 901). wnfidence level requires 64 subjects. Decrease in confidence affecte sample size as A. Decreasing the unfidence Level decreases the sample size needed. On calculating a N 156 ܦܠ 64

Statkey Theoretical Distribution Normal Distribution Reset Plot Normal Distribution Left Tail Two-Tail Right Tail Mean Standard Deviation 0.40 0 1 0.35 Edit Parameters 0.30 0.25 0.20 0.0050 0.990 0.0050 0.15 0.10 0.05 0.00 -4.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 4.0 -2.576 2.576 Activate Windows

Statkey Theoretical Distribution Normal Distribution Reset Plot Normal Distribution Left Tail Two-Tail Right Tail Mean 0.40 Standard Deviation 0 0.35 Edit Parameters 0.30 0.25 0.20 0.050 0.900 0.050 0.15 0.10 0.05 0.00 -4.0 -3.0 -1.0 0.0 1.0 2.0 3.0 4.0 -2.0 -1.645 1.645 Activate Windows

The sample size is calculated using the formula mentioned. The critical values are obtained from STATKEY (image attached for reference). Decreasing the confidence level decreases the sample size.