Math Problem Statement

A variable has a mean of 100 and a standard deviation of 6. Four observations of this variable have a mean of 119 and a sample standard deviation of 8. z= , t =

Solution

To calculate the z-score and t-score, we need to clarify which of the two sets of data you're referencing.

1. Z-Score:

The z-score measures how many standard deviations an observation is from the population mean. It is used when the population standard deviation is known.

The formula for the z-score is:

z=Xμσz = \frac{X - \mu}{\sigma}

Where:

  • XX is the sample mean
  • μ\mu is the population mean
  • σ\sigma is the population standard deviation

In your case:

  • X=119X = 119 (sample mean)
  • μ=100\mu = 100 (population mean)
  • σ=6\sigma = 6 (population standard deviation)

Substitute the values:

z=1191006=1963.17z = \frac{119 - 100}{6} = \frac{19}{6} \approx 3.17

So, the z-score is approximately 3.17.

2. T-Score:

The t-score is used when the population standard deviation is unknown, and we only have the sample standard deviation. It is computed using:

t=Xμsnt = \frac{X - \mu}{\frac{s}{\sqrt{n}}}

Where:

  • X=119X = 119 (sample mean)
  • μ=100\mu = 100 (population mean)
  • s=8s = 8 (sample standard deviation)
  • n=4n = 4 (sample size)

Now substitute the values:

t=11910084=1982=194=4.75t = \frac{119 - 100}{\frac{8}{\sqrt{4}}} = \frac{19}{\frac{8}{2}} = \frac{19}{4} = 4.75

So, the t-score is 4.75.

Summary:

  • z-score: 3.17\approx 3.17
  • t-score: 4.754.75

Let me know if you'd like more details or have any further questions!

5 related questions:

  1. What is the difference between a z-score and a t-score?
  2. When should you use a t-distribution instead of a normal distribution?
  3. How does sample size affect the t-distribution?
  4. What happens to the t-score if the sample size increases?
  5. Can we use a z-score when the population standard deviation is unknown?

Tip:

For small sample sizes (typically n30n \leq 30), use the t-distribution since it accounts for more uncertainty in estimating the population parameters.

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Math Problem Analysis

Mathematical Concepts

Statistics
Z-Score
T-Score
Normal Distribution
T-Distribution

Formulas

z = (X - μ) / σ
t = (X - μ) / (s / √n)

Theorems

Central Limit Theorem
Properties of Z-Distribution
Properties of T-Distribution

Suitable Grade Level

Grades 10-12