Chapter 8: Interval Estimation Flashcards
Confidence Interval
a range of values constructed around a sample statistic that estimates the parameter
AKA: Interval Estimate
Confidence Limit
Lower and upper bounds of a confidence interval
3 -Parts of a Confidence Interval
- Confidence Level (%)
- Point Estimate
- Margin of Error
Margin of Error
The largest possible distance between the statistic and the parameter
(critical value)(standard error)
Confidence Level
the percentage of intervals that will contain the parameter given a statistic
Confidence Coefficient
The confidence level as a proportion
⍺
- the level of error you are willing to accept
- the area in the tails
AKA: Significance level
As ⍺ gets smaller →
it becomes more “strict” or “stringent” and the “specificity” of the interval decreases
Critical Value
z-scores that correlate to the confidence limits
Critical Probability
Area below a z-score
Critical Value for a 99% CI
⍺ = 0.01
CV = +/- 2.576
Estimating Sample Size Without σ
- s
- range / 4
T-Distribution v. Z-Distribution (3)
- variance of the t-distribution > 1
- t-distribution is a family of curves
- as the sample size increases, the t-distribution approaches the z-distribution
Sample Size and Critical Values (t-table)
as the sample size increases → the critical value decreases → margin of error decreases → CI becomes smaller
Degrees of Freedom
n-1