Statistics Chapter 8 - Confidence Intervals

The flashcards below were created by user honestkyle on FreezingBlue Flashcards.

  1. What is the status of Image Upload 1 for z-based confidence intervals for a population mean?
    Image Upload 2 is known
  2. What is the status of Image Upload 3 for t-based confidence intervals for population mean?
    Image Upload 4 is unknown
  3. What two things does Statistical Inference involve?
    • Estimation
    • Hypothesis
  4. What do we use statistical inferences for?
    To make inferences about a parameter
  5. What are the two types of estimates of parameters?
    • Point estimate
    • Interval estimate
  6. What is a Interval Estimate?
    It's a point estimate with a +/- Margin of Error
  7. What is the purpose of an Interval Estimate?
    Provide info about how close the point estimate is to the parameter
  8. In an Interval Estimate, what does the Width depend on?
    How much confidence you want in your estimate
  9. What is Precision?
    Width of an interval
  10. What is Accuracy?
    Probability of the estimate being correct, defined as Image Upload 5
  11. What is the general form of the interval estimate for the population mean?
    Image Upload 6+/- Margin of Error
  12. What is the interval estimate of Image Upload 7 equation if Image Upload 8 is known?
    Image Upload 9
  13. What is Image Upload 10?
    The confidence coefficient
  14. What is Image Upload 11?
    The z-value that provides an area of Image Upload 12 in the upper tail of the standard normal prob distribution
  15. Assume:
    Population of all individual car mileages is ND
    Standard deviation (Image Upload 13) is 0.8
    A sample size (n) of 50
    Build a 95% interval estimate of Image Upload 14
    • We have 95% confidence that Image Upload 15 will be within +/- .22 mpg of the population mean
    • Image Upload 16
    • Image Upload 17 (from z-table)
    • Margin of error = (1.96)(.113) = .22
  16. If we have 95% confidence that Image Upload 18 will be within +/- .22 mpg of the population mean...
    Assume Image Upload 19 = 31.56
    What is the confidence interval?
    [31.56 +/- 0.22] = [31.34, 31.78]
  17. If Image Upload 20 = 0.10 (90% confidence) what is the confidence interval width?
    1.645
  18. If Image Upload 21 = 0.05 (95% confidence) what is the confidence interval width?
    1.96
  19. If Image Upload 22 = 0.01 (99% confidence) what is the confidence interval width?
    2.576
  20. What probability of values is between z-scores of -1.645 and +1.645?
    0.9000
  21. What probability of values is between z-scores of -1.96 and +1.96?
    0.9500
  22. What probability of values is between z-scores of -2.576 and +2.576?
    0.9900
  23. What is used instead of Image Upload 23 when it is not known?
    • s
    • Sample standard deviation
  24. What is the t-score standard error equation?
    Image Upload 24
  25. What is the t-score equation?
    Image Upload 25
  26. What are the differences between the t-distribution and the z-distribution?
    • t-distribution is more spread out than the standard normal (z-distribution)
    • t-distribution is defined by the # of degrees of freedom (df = n - 1)
  27. What happens to the degrees of freedom (df) as n (sample size) increases?
    df increases
  28. What happens to the t-curve as the degrees of freedom (df) increases?
    • t-curve narrows
    • Spread decreases
    • Eventually approaches the standard normal curve
  29. At what sample size does the t-curve become very similar to the z-curve?
    Image Upload 26
  30. At what sample size is the z-distribution used INSTEAD of the t-distribution?
    Image Upload 27
  31. What's the differences between the t-table and the z-table?
    • t-table shows values to the RIGHT of the t-score
    • t-table is based on df and not n
  32. What is the Confidence Interval equation for the t-distribution (Image Upload 28 is not known)?
    Image Upload 29
  33. In a sample of 16 management consultants, the following statistics about hourly wages have been computed:
    Image Upload 30
    Image Upload 31
    Construct a  95% confidence interval (C.I.) estimate.
    Image Upload 32

    • Image Upload 33
    • Image Upload 34

    • Image Upload 35
    • Image Upload 36
Author:
honestkyle
ID:
211890
Card Set:
Statistics Chapter 8 - Confidence Intervals
Updated:
2013-04-11 18:51:02
Tags:
confidence intervals probability stats
Folders:

Description:
Confidence Intervals
Show Answers: