A distribution has a mean of 40 and a standard deviation of 5. 68% of the distribution can be found between what two numbers?

68% of the distribution is within one standard deviation of the mean. 40 + 5 = 45, 40 - 5 = 35
false
30 and 50
false
0 and 45
false
0 and 68
true
35 and 45
A distribution has a mean of 20 and a standard deviation of 3. Approximately 95% of the distribution can be found between what two numbers?

95% of the distribution is within 1.96 standard deviations of the mean. You can round 1.96 to 2 to approximate. 20 - 2(3) = 14, 20 + 2(3) = 26
false
17 and 23
true
14 and 26
false
10 and 30
false
0 and 23
A normal distribution has a mean of 5 and a standard deviation of 2. What proportion of the distribution is above 3?

.8413
0.002
Use the "Calculate Area for a given X" calculator and enter Mean = 5, SD = 2, Above 3. You will get 0.8413.
A normal distribution has a mean of 120 and a variance of 100. 35% of the area is below what number?

116.1468
0.05
Var = 100, so SD = 10. Use the "Calculate X for a given Area" calculator and enter Mean = 120, SD = 10, Shaded area = .35. Click below, and you will get 116.15.
A normal distribution of test scores has a mean of 38 and a standard deviation of 6. Everyone scoring at or above the 80th percentile gets placed in an advanced class. What is the cutoff score to get into the class?

43
0.05
Use the "Calculate X for a given Area" calculator and enter Mean = 38, SD = 6, Shaded area = .80. Click below, and you will get 43.05, meaning a score of 43.
A normal distribution of test scores has a mean of 38 and a standard deviation of 6. What percent of the students scored between 30 and 45?

78.7
0.3
Use the "Calculate Area for a given X" calculator and enter Mean = 38, SD = 6, Between 30 and 45. You will get 0.787, meaning 78.7%.