Confidence Intervals

Question 1

Sampling distribution of the mean (summary)

Answer 1

Shows a normal distribution where the middle is the mean of the sampling distribution
- The sampling distribution is an idealised frequency distribution
- Mean of sampling distribution is µ

Question 2

What is the significance of the SEM

Answer 2

Indicates how much variation is likely to be between the mean of a sample and the true population mean

Question 3

Normal distribution

Answer 3

• Symmetrical
• Mean is the centre
  50% of the distribution above and below the mean
• Has well established properties which allow researchers to complete inferential tests and confidence intervals

Question 4

Confidence level and corresponding Z-score

Answer 4

90% is 1.645
95% is 1.96
99% is 2.576
99.99% is 3.890

Question 5

Point estimation of µ

Answer 5

The sample mean M is the pest point of estimation µ because M is an unbiased estimator of µ

Question 6

Interval estimate of µ

Answer 6

Construct a range of valves which we believe, with a certain level of confidence, covers the true value of µ (confidence interval)

Question 7

What is alpha

Answer 7

Typically refers to the error rate which is allowed

• A lower error rate = higher confidence

Question 8

What are the critical values

Answer 8

Specific points on a distribution that define the boundaries of a rejection region

Question 9

What is the effect of confidence level on the width of the interval

Answer 9

The greater the level of confidence (How certain we are) the wider the interval (The range we estimate)