At Gnomes-Are-Us, the weekly output of garden gnomes over a four-week period is thus: Week 1: 900 gnomes, Week 2: 1100 gnomes, Week 3: 900 gnomes, Week 4: 1100 gnomes. What is the weekly mean (or average) and the standard deviation from the mean?
A) Mean: 1000; Standard deviation: 100
B) Mean: 1200; Standard deviation: 50
C) Mean: 750; Standard deviation: 75
D) Mean: 1000; Standard deviation: 200



Answer :

Answer:

A) Mean: 1000; Standard deviation: 100

Step-by-step explanation:

In four weeks the weekly outputs are
Week 1: 900
Week 2: 1100
Week 3: 900
Week 4: 1100

Total for 4 weeks: 900 + 1100 + 900 + 1100 = 4,000

Weekly mean = Total/number of weeks = 4000/4 = 1000

The variance from the mean, [tex]\sigma^2[/tex]  is the sum of the squares of the deviations from the mean divided by the total number of observations

[tex]\sigma^2 = \dfrac{(900 - 1000)^2 + (1100-1000)^2 + (900-1000)^2 + (\\1100- 1000)^2}{4}\\= \dfrac{100^2 + 100^2 + 100^2 + 100^2}{4}\\= \dfrac{4 \cdot 100^2}{4}\\\\= 100^2\\\\[/tex]

The standard deviation from the mean,  [tex]\sigma[/tex], is the square root of the variance

[tex]\sigma = \sqrt{100^2} = 100 \quad\text{since $\sqrt{x^2} =x$}[/tex]

Mean = 1000

Standard deviation = 100


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