A typical adult has an average IQ score of 105 with a standard deviation of 20. If 20 randomly selected adults are given an IQ test, what is the probability that the sample mean scores will be between 85 and 125 points?
For x = 125, our z-score and probability is seen here
Z = 1
P(x < 1) = 0.841345
For x = 85, our z-score and probability is seen here
Z = -1
P(x < -1) = 0.158655
So what we want is the probability between these values:<br />
0.841345 - 0.158655 = 0.68269
For x = 125, our z-score and probability is seen here
Z = 1
P(x < 1) = 0.841345
For x = 85, our z-score and probability is seen here
Z = -1
P(x < -1) = 0.158655
So what we want is the probability between these values:<br />
0.841345 - 0.158655 = 0.68269