Stat 301 – Day 27 Sign Test

Last Time – Prediction Interval When goal is to predict an individual value in the population (for a quantitative variable) rather than the population mean. Technical conditions  Need random sample  Need normal population

PP (p. 364) t 129 = 1.98 for 95% confidence (.733) = = (96.78, 99.72). We are 95% confident that a healthy adult’s body temperature will be between o F and o F. Temperatures outside this range should be cause for concern.

“Paired t-test” When you have two quantitative measurements on each observational unit (e.g., pre-test, post-test), take the differences and carry out one-sample t-procedures on the differences  “Gets rid of” person to person variability  Parameter = population mean difference  Technical conditions are about the differences

PP (p. 364) 95% confidence interval for  : Variable N Mean StDev SE Mean 95% CI diffs ( , ) We are 95% confident that the mean volume difference between the unaffected and affected twins is between.0667 and Valid?

Quiz 22

Choice of Procedure (p. 382) Binary response Parameter:  p-value from normal, binomial, or hypergeometric Adjusted Wald CI Quantitative response Parameter:  p-value from t distribution Confidence interval vs. prediction interval

Example What is a typical backpack-body weight ratio? Do most students have a low enough ratio?

For tomorrow Review questions/example questions in Blackboard