Q8 Homework

Research Methods -- CRJU 3601 – Homework Answers

Validity and Reliability in Research (95% Confidence Interval)

Practice for the 95% Confidence Interval

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Problem 1. A researcher wants to be 95% certain that the means shown below are accurate. That means she must find the raw score below the mean that encompasses 47.5% of the scores, and the raw score above the mean that encompasses 47.5% of the scores. 47.5% + 47.5% = 95%. Create a 95% confidence interval around the following means and standard deviations:

a. = 100, s = 15 b. = 500, s = 100 c. = 50, s = 10,

d. = 41, s = 8 e. = 0, s = 1 f. = 5.5, s = 0.5

Problem 2. What two raw scores encompass the 95% confidence interval around the mean of 42 Standard Deviation of 18?

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Answer Problem 2. 77.28 and 6.72

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Problem 3. In order to qualify for points toward promotion, an officer must not be over or under 1.96 standard deviations from the overall mean of 200. The standard deviation is 35. What is the lowest score a soldier can have and still qualify for points? a. 168 b. 131 c. 104 d. 269

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Answer Problem 3. 131

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Problem 4. A random sample produced a mean 8,000 with a standard deviation of 2500. What two raw scores provide the 95% confidence interval?

a. 3100-12900 b. 3300-11000 c. 2200-10000 d. 4500-14500

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Answers Problem 4. 3100-12900