Session Ready
Exercise

Calculating a Confidence Interval Without The Population Standard Deviation

Unfortunately in reality we usually don't know a population standard deviation, and thus must rely on sample standard deviations and T-scores. T-scores come from T-distributions, which help us account for error that occurs when we sample from a population. We use a different T-distribution to calculate cumulative probabilites depending on our degrees of freedom.

Lets say we conducted another study on how often people get angry when they're driving (known as 'road rage') using a sample of 200 people chosen at random, saved in your console as rrage. Let's calculate the 95% confidence interval for where the population mean lies.

This time we must use a slightly different formula: sample mean +/- t value * standard error. The standard error is calculated as the population standard deviation, divided by the square root of the sample size. The T-score for a df of 199 is 1.9720.

Instructions
100 XP
  • The road rage level of each participant in your sample is saved in your console as rrage
  • Complete the steps in your script to calculate the confidence interval for rrage
  • Remember to format your calculations correctly and use () where appropriate