Calculating Delta Values: Paired t Test

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In summary, the conversation discusses using a paired t test to compare results and calculate delta values for pollution levels. The question arises of how to pair the results, and it is suggested to use the deltas for the same day and perform a one-tailed t-test with a null hypothesis of a mean delta greater than 4 mg/L. The relevance of comparing April and September as two populations is questioned.
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lamlam1
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upload_2019-3-10_21-59-57.png


Using paired t test, how should I pair these results?
To calculate the delta values, should I use: downstream - upstream for both sep and apr ?
or upstream (sep) - upstream (apr) and downstream (sep) - downstream (apr) ?

Thanks
 

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  • #2
What is the quantity that you want to test and which pairing gives you that quantity?
 
  • #3
How do you get a net pollution value? Is there a typo on increasing pollution? Shouldn't it be lowering pollution?
 
  • #4
lamlam1 said:
View attachment 240043

Using paired t test, how should I pair these results?
To calculate the delta values, should I use: downstream - upstream for both sep and apr ?
or upstream (sep) - upstream (apr) and downstream (sep) - downstream (apr) ?

Thanks

Only the delta for the same day makes sense as the concern is an upper limit of 4 mg/L increase. Not sure why comparing April and Sep as two populations is relevant, seems to me a one tailed t-test on the delta with a null hypothesis that the mean of the delta >4 would be the relevant test
 
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What is a paired t test?

A paired t test is a statistical method used to compare the means of two related groups or conditions. It is often used in scientific research to determine if there is a significant difference between two sets of data.

How do you calculate delta values for a paired t test?

To calculate delta values for a paired t test, you first need to find the difference between the paired observations. Then, you take the average of these differences and divide it by the standard deviation of the differences. This will give you the delta value, which is used in the t test formula to determine the significance of the difference between the two groups.

What is the purpose of calculating delta values in a paired t test?

The purpose of calculating delta values in a paired t test is to determine the magnitude of the difference between the two groups or conditions being compared. This helps to determine if the difference is statistically significant or if it is due to chance.

What are the assumptions of a paired t test?

The assumptions of a paired t test include: 1) the data is normally distributed, 2) the variances of the two groups are equal, 3) the observations within each pair are independent of each other, and 4) the difference between the two groups is normally distributed.

When should a paired t test be used instead of an unpaired t test?

A paired t test should be used when the two groups being compared are related or paired in some way, such as before and after measurements on the same individuals. An unpaired t test should be used when the two groups are independent of each other, such as two different groups of individuals.

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