A rule of thumb for normal distributions is the following:
ï‚· Approximately 68% of observations are within 1 standard deviation of the mean
Approximately 95% of observations are within 2 standard deviations of the mean
Approximately 99.7% of observations are within 3 standard deviations of the mean
Use the 68-95-99.7 rule to approximate the following percentages:


3. The percentage of days less than 68.4 degrees.

4. The percentage of days greater than 72.6 degrees.