6.3. Standard Deviation of a Data Set http://www.ck12.org
TABLE6.21:
Data(x) Mean(x ̄) Data−Mean(x−
x ̄)Square of Data −
Mean(x−x ̄)^2∑
- Suppose data are normally distributed, with a mean of 100 and a standard deviation of 20. Between what 2
values will approximately 68% of the data fall?
a. 60 and 140
b. 80 and 120
c. 20 and 100
d. 100 and 125 - The sum of all of the deviations about the mean of a set of data is always going to be equal to:
a. positive
b. the mode
c. the standard deviation total
d. 0 - Suppose data are normally distributed, with a mean of 50 and a standard deviation of 10. Between what 2
values will approximately 95% of the data fall?
a. 40 and 60
b. 30 and 70
c. 20 and 80
d. 10 and 95 - If data are normally distributed, what percentage of the data should lie within the range ofμ± 3 σ?
a. 34%
b. 68%
c. 95%
d. 99.7% - If a normally distributed population has a mean of 75 and a standard deviation of 15, what proportion of the
values would be expected to lie between 45 and 105?
a. 34%
b. 68%
c. 95%
d. 99.7% - If a normally distributed population has a mean of 25 and a standard deviation of 5.5, what proportion of the
values would be expected to lie between 19.5 and 30.5?
a. 34%
b. 68%
c. 95%
d. 99.7%