Math Problem Statement

A random sample of students was asked how many lectures they had attended in the previous week.

Their responses where: 4, 3, 0, 4, 5, 3, 2, 5, 3, 1, 4, 5.

What is the sample standard deviation for the number of lectures attended, to 1 decimal place?

Solution

To calculate the sample standard deviation, we will use the formula for sample standard deviation:

s=(xixˉ)2n1s = \sqrt{\frac{\sum (x_i - \bar{x})^2}{n - 1}}

Where:

  • xix_i are the data points,
  • xˉ\bar{x} is the sample mean,
  • nn is the number of data points.

Step 1: Find the sample mean (xˉ\bar{x})

The data points are: 4,3,0,4,5,3,2,5,3,1,4,54, 3, 0, 4, 5, 3, 2, 5, 3, 1, 4, 5

First, find the sum of the data points: Sum=4+3+0+4+5+3+2+5+3+1+4+5=39\text{Sum} = 4 + 3 + 0 + 4 + 5 + 3 + 2 + 5 + 3 + 1 + 4 + 5 = 39

Next, calculate the mean: xˉ=Sumn=3912=3.25\bar{x} = \frac{\text{Sum}}{n} = \frac{39}{12} = 3.25

Step 2: Calculate each squared difference from the mean

Now, calculate the difference between each data point and the mean, square it, and sum them up.

(43.25)2=0.5625,(33.25)2=0.0625,(03.25)2=10.5625(4 - 3.25)^2 = 0.5625, \quad (3 - 3.25)^2 = 0.0625, \quad (0 - 3.25)^2 = 10.5625 (43.25)2=0.5625,(53.25)2=3.0625,(33.25)2=0.0625(4 - 3.25)^2 = 0.5625, \quad (5 - 3.25)^2 = 3.0625, \quad (3 - 3.25)^2 = 0.0625 (23.25)2=1.5625,(53.25)2=3.0625,(33.25)2=0.0625(2 - 3.25)^2 = 1.5625, \quad (5 - 3.25)^2 = 3.0625, \quad (3 - 3.25)^2 = 0.0625 (13.25)2=5.0625,(43.25)2=0.5625,(53.25)2=3.0625(1 - 3.25)^2 = 5.0625, \quad (4 - 3.25)^2 = 0.5625, \quad (5 - 3.25)^2 = 3.0625

Summing these squared differences: Sum of squared differences=0.5625+0.0625+10.5625+0.5625+3.0625+0.0625+1.5625+3.0625+0.0625+5.0625+0.5625+3.0625=27.194\text{Sum of squared differences} = 0.5625 + 0.0625 + 10.5625 + 0.5625 + 3.0625 + 0.0625 + 1.5625 + 3.0625 + 0.0625 + 5.0625 + 0.5625 + 3.0625 = 27.194

Step 3: Apply the formula

Now we divide by n1n - 1 (where n=12n = 12): 27.194121=27.19411=2.472\frac{27.194}{12 - 1} = \frac{27.194}{11} = 2.472

Finally, take the square root to find the sample standard deviation: s=2.4721.6s = \sqrt{2.472} \approx 1.6

Conclusion

The sample standard deviation is approximately 1.6.

Would you like further details or have any questions?


Here are five related questions you could explore:

  1. How does sample standard deviation differ from population standard deviation?
  2. What are the effects of adding or removing a data point on the sample standard deviation?
  3. How would the calculation change if one data point were an outlier, like 10?
  4. How does standard deviation relate to variance?
  5. How is the sample mean different from the population mean in terms of usage?

Tip: Always check whether you need sample or population standard deviation, as the formula changes slightly.

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Math Problem Analysis

Mathematical Concepts

Statistics
Sample Standard Deviation
Measures of Dispersion

Formulas

Sample standard deviation: s = sqrt((Σ(x_i - x̄)^2) / (n - 1))
Mean (x̄): x̄ = Σx_i / n

Theorems

Law of Large Numbers (implicitly related in sampling)

Suitable Grade Level

Grades 9-12