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Find the critical t-value that corresponds to 80% confidence with 24 degrees of freedom.
alpha = 0.2, so t_alpha/2 = t_alpha/2 = t_0.2/2 = t_0.10
TI-84: Stats --> Tests --> option 4
PRGRM --> Area Left = .9 --> DF --> 24
Same as invNorm function, but for samples, not populations.
Name the two t-interval construction requirements:
1) Normal probability plot suggests a normal population based in ctirical values of the correlation coefficient vs. correlation coefficient.
2) No outliers in boxplot
In confidence intervals...
if sample size is < 30, what conditions must be satisfied to compute the Confidence Interval?
Sample data must come from a population that is normally distributed with no outliers.
Confidence Interval requirements are:
Confidence Interval for Population Mean:
Use Stat --> Tests --> option 4
PRGRM, where n-1 = degrees of freedom
Use formula above after using calc to find value
Confidence Interval for Population Parameter:
Use Stat --> Tests --> Option 8 (T-test)
Sample size is asked for:
For "E", do not use decimal points in this formula. Use the value given for "points".
For Confidence Intervals for standard deviation when s2 is given, do NOT use the square root part of the function, just the formula inside the square root.
Know Reasoning Questions (e.g., What happens to a confidence interval if you increase the sample size?)
Use 1-PropZtest on TI-84 for __________ _____ for proportions.
Requirements to construct a hypothesis tests are three:
- 1) SRS
- 2) np(1-p)>=10
- 3) n<0.05N
n ____ increase by a factor of _ to ________ E by a factor of ___.
must, 9, decrease, 1/3
Define "Margin of Error"
the amount the estimate based on the sample data could be away from the true percentage with a certain level of confidence.
This is HALF the width of the confidence interval.
Define "Critical Value":
number of standard errors to move from the mean of a sampling distribution to correspond to a specified level of confidence.
in place of
to find "n" for a proportion when IS GIVEN.
For confidence interval estimates for the population mean
- 1) SRS
- 2) n>=30 or approximately normally distributed
TI-84: Use T-Interval (Stat, Tests, Option 8)