A.9 Mean Absolute and Standard Deviation Practice
Mr. Hannam
Name __________________________________________ Date__________________ Block_______
Variance (σ2) and Standard Deviation (σ)
By Hand:




Find mean (μ)
Find the distances each data point is away from the mean
(deviation). Square each of these distances.
Take the mean of these distances to get variance (σ2).
Take the square root of variance to get standard deviation (σ).
Formulas:
n
n

σ2 =
 ( xi   ) 2
i 1
n
,σ=
 (x
i 1
i
 )2
n
If you have a graphing calculator:

put the data points in L1 and calculate the mean (STAT/CALC)

read σx from the calculator (NOT Sx)!

square σx to get variance (square VARS:5:4 to get exact value!)
Find the mean absolute deviation (MAD), variance (σ2), and standard deviation (σ) for the
data sets below. Round to the nearest hundredth if necessary. Do the first 3 standard
deviations by hand in addition to using the calculator. Use the calculator for the rest.
Show all work!
1) {8, 4, 6, 5, 6, 6, 9, 4, 8, 4} 2) {86, 100, 94, 96, 88, 94}
μ = _________
μ = _________
3) {15, 20, 35, 40, 12, 19, 10, 9}
μ = _________
distances from mean:
distances from mean:
distances from mean:
____________________
____________________
____________________
MAD = __________
MAD = __________
MAD = __________
σ2 = ______________
σ2 = ______________
σ2 = ______________
σ = _______________
σ = _______________
σ = _______________
4) {45, 53, 55, 48, 40, 59}
5) {-5, -3, 0, 1, 4, 4, 5, -2, 1} 6) {21.4, 22.8, 19.2, 20.5, 18.3}
μ = _________
μ = _________
μ = _________
distances from mean:
distances from mean:
distances from mean:
____________________
____________________
____________________
MAD = __________
MAD = __________
MAD = __________
σ2 = ______________
σ2 = ______________
σ2 = ______________
σ = _______________
σ = _______________
σ = _______________