Sampling Distribution of Differences

Understand the sampling distribution of differences between means—what it is, why it matters, and how to apply it in hypothesis testing (with examples). Perfect for students, data scientists, and analysts! Ever wondered how statisticians compare two groups (e.g., test scores, sales performance, or medical treatments)? The key lies in the sampling distribution of differences between means—a fundamental concept for hypothesis testing, confidence intervals, and A/B testing.

Sampling Distribution of Differences Between Means

The Sampling Distribution of Differences Between Means is the probability distribution of differences between two sample means (e.g., MeanAMeanB) if you repeatedly sampled from two populations.

Let there are two populations of size N1 and N2 having means μ1 and μ2 with variances σ12 and σ22. We need to draw all possible samples of size n1 from the first population and n2 from the second population, with or without replacement.

Let x1 be the means/averages of samples of the first population and x2 be the means/averages of the samples of the second population. After this, we will determine all possible differences between means/averages denoted by
d=x1x2

We call the frequency distribution differences as frequency distribution, while the probability distribution of the differences is the sampling distribution of differences between means.

Notations for Sampling Distribution of Differences between Means

NotationShort Description
μ1Mean of the first population
μ2Mean of the second population
σ12Variance of the first population
σ22Variance of the second population
σ1Standard deviation of the first population
σ2Standard deviation of the second population
μx1x2Mean of the sampling distribution of difference between means
σx1x22Variance of the sampling distribution of difference between means
σx1x2Standard deviation of the sampling distribution of difference between means

Some Formulas for Sampling with/without Replacement

Sr. No.Sampling with ReplacementSampling without Replacement
1.μx1x2=μ1μ2μx1x2=μ1μ2
2.σx1x22=σ12n1+σ22n2σx1x22=σ12n1(N1n2N11)+σ22n2(N2n2N21)
3.σx1x2=σ12n1+σ22n2σx1x2=σ12n1(N1n2N11)+σ22n2(N2n2N21)

Example

Let x represent the mean of a sample of size n1=2 selected at random with replacement from a finite population consisting of values 5, 7, and 9. Similarly, let x2 represent the mean of a sample of size n2=2 selected at random from another finite population consisting of values 4, 6, and 8. Form the sampling distribution of the random variable x1x2 and verify that

  • μx1x2=μ1μ2
  • $\sigma^2_{\overline{x}_1 – \overline{x}_2} = \frac{\sigma_1^2}{n_1}+\frac{\sigma_2^2}{n_2}

Solution

Population IPopulation II
5, 7, 9
N1=3
n1=2
4, 6, 8
N2=3
n2=2
Possible samples with Replacement are N1n1=32=9Possible samples with Replacement are
N2n2=32=9
Sampling Distribution of Differences Between Means

All Possible Samples

All possible differences between samples means from both of the population is (d=x1x2).

d=x1=x2455666778
55-4= 100-1-1-1-2-2-3
6211000-1-1-2
6211000-1-1-2
732211100-1
732211100-1
732211100-1
8433222110
8433222110
9544333221

The Sampling Distribution of Differences Between Means

d=x1x2fP(d)dP(d)d2d2P(d)
-311/8131/81=3/8199/81
-244/81-8/81416/81
-11010/81-10/81110/81
01616/810/8100/81
11919/8119/81119/81
21616/8131/81464/81
31010/8130/81990/81
444/8116/811664/81
511/815/8125125/81
Total8181/81=1 297/81=3.67

μx1x2=E(d)=Σ(dP(d))=8181=1σx1x22=E(d2)[E(d)]2=Σd2P(d)[Σ(dP(d))]2=3.6712=2.67

Sampling Distribution of differences between means, mean and variance of both populations

Verification

  • μx1x2=μ1μ276=1
  • σx1x22=σ12n1+σ22n2=2.662+2.6622.66

Sampling in R Language

Excel Power Query Questions 16

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Online MS Excel Power Query Questions with Answers

1. In which Microsoft applications can Power Query be used?

 
 
 
 

2. What happens when you disable “Load” for a query in Power Query Editor?

 
 
 
 

3. How can you remove duplicates in Power Query?

 
 
 
 

4. A Merge Query performs a similar functionality to some Excel functions. Which functions are they?

 
 
 
 

5. What is Power Query primarily used for?

 
 
 
 

6. Suppose that we have two queries containing two employment data sets. Each data set has the historical employee details of two subsidiary companies of the same parent organisation. What type of join is required to find out the employees who have worked in both organisations?

 
 
 
 
 
 

7. What is the M language in Power Query?

 
 
 
 

8. What does the “Group By” feature in Power Query allow you to do?

 
 
 
 

9. How can you handle errors (e.g., division by zero) in Power Query?

 
 
 
 

10. What is a “Query Step” in Power Query?

 
 
 
 

11. What does “Unpivot Columns” do in Power Query?

 
 
 
 

12. Where does Power Query store its transformation steps?

 
 
 
 

13. What could you do if you needed to merge three queries?

 
 
 

14. Which of the following is NOT a data source in Power Query?

 
 
 
 

15. How do you refresh data in Power Query?

 
 
 

16. What is the purpose of the “Parameters” feature in Power Query?

 
 
 
 

17. Which Power Query feature allows combining data from multiple sources?

 
 
 
 

18. For a Merge Query to work, we do not need the column headings to match; however, we do need the values of one column in one query to relate to the values of a column in the other query.

 
 

19. Which Power Query operation would you use to split a single column into multiple columns?

 
 
 
 

20. If you have a query that displays the output from a Right Anti Join, the last few characters of the M code in the formula bar will read JoinKind.RightAnti. What will happen if we edit the text in the formula bar to replace JoinKind.RightAnti with JoinKind.RightOuter and press Enter?

 
 
 
 

Online Excel Power Query Questions Quiz

  • A Merge Query performs a similar functionality to some Excel functions. Which functions are they?
  • For a Merge Query to work, we do not need the column headings to match; however, we do need the values of one column in one query to relate to the values of a column in the other query.
  • Suppose that we have two queries containing two employment data sets. Each data set has the historical employee details of two subsidiary companies of the same parent organisation. What type of join is required to find out the employees who have worked in both organisations?
  • What could you do if you needed to merge three queries?
  • If you have a query that displays the output from a Right Anti Join, the last few characters of the M code in the formula bar will read JoinKind.RightAnti. What will happen if we edit the text in the formula bar to replace JoinKind.RightAnti with JoinKind.RightOuter and press Enter?
  • What is Power Query primarily used for?
  • In which Microsoft applications can Power Query be used?
  • Which Power Query feature allows combining data from multiple sources?
  • What is the M language in Power Query?
  • How do you refresh data in Power Query?
  • What does “Unpivot Columns” do in Power Query?
  • Which of the following is NOT a data source in Power Query?
  • What is a “Query Step” in Power Query?
  • How can you remove duplicates in Power Query?
  • Where does Power Query store its transformation steps?
  • What does the “Group By” feature in Power Query allow you to do?
  • Which Power Query operation would you use to split a single column into multiple columns?
  • What is the purpose of the “Parameters” feature in Power Query?
  • How can you handle errors (e.g., division by zero) in Power Query?
  • What happens when you disable “Load” for a query in Power Query Editor?

Learn about the R Programming Language

Conditional Formatting Excel Quiz 15

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Online Trend Based Conditional Formatting Excel Quiz with Answers
Please go to Conditional Formatting Excel Quiz 15 to view the test

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Statistics For Data Analyst