You cannot just add the standard deviations.
Instead, you add the variances. Those are built up from the squared differences between every individual value from the mean (the squaring is done to get positive values only, and for other reasons, that I won't delve into).
Standard deviation is defined as the square root of the variance .
The other way around, variance is the square of SD.
- You square the individual SD's to get the variances
- Then you add these together to get the total variance
- Then you take the square root to get the total SD
A population of values has a normal distribution with
Find the probability that a single randomly selected value is between 133.6 and 134.1.
Write your answers as numbers accurate to 4 decimal places.
We wish to estimate what percent of adult residents in a certain county are parents. Out of 600 adult residents sampled, 192 had kids. Based on this, plot a
Express your answer in the form of three inequalities. Give your answers in decimal fractions up to three places