# Recent content by obh

1. ### Can someonedy solve this? I have to submit it in one hour

You can have the results in the following calculator link You also have the formulas at the bottom of the link. It is better that you will calculate yourself and check the results with the calculator. http://www.statskingdom.com/180Anova1way.html
2. ### What statistical test would best suit my data?

Hi CMS What outcome do you want to check? I assume you compare period before removing the incentive, to period after? What timeframe do you check? If you want to compare the average of the outcome before, to the average of the outcome after, the default test is paired T-test.
3. ### Homogeneity requirements for Linear regression

Correct, for example, CLT (if relevant ...) doesn't always work, try to do CLT on data with undefined skewness like F(3,3). the sample average will be skewed also for a huge sample size.
4. ### Homogeneity requirements for Linear regression

Is there a "common" number, that from this number and larger, it is less important to check the "homogeneity of the variances" ?
5. ### Assumption of Manova?

https://ncss-wpengine.netdna-ssl.com/wp-content/themes/ncss/pdf/Procedures/NCSS/Multivariate_Analysis_of_Variance-MANOVA.pdf
6. ### Assumption of Manova?

Hi Ghoza, In MANOVA the assumption is for multivariate normality, which is difficult to check. You may check separately the normality of each DV for the IVs, not as good bu practically used. but if you have at list 20 observations for each combination of dependent*independent variable. you...
7. ### Assumption of Manova?

Generally in ANOVA or Regression the normality assumption is for the residuals. So I assume the same for MANOVA. (the same as linear regression) ANOVA test shouldn't be sensitive for moderate deviation from the normality when the sample size is big enough (CLT)
8. ### Homogeneity requirements for Linear regression

Hi Greta, From what sample size the "homogeneity of the variances" assumption is not important for linear regression? I assume it is the same for ANOVA.?
9. ### Dealing with definition changes mid time series

Hi Klik, You probably have two options. If you know the way the counting was changed, you may adjust the old data count to the new count. Otherwise you may analyze the old data or the new data, or both separately

Hi Youssef, The following will show you how to calculate Mean, Mode, Median, Standard deviation, and will also calculate based on your numbers http://www.statskingdom.com/20median.html http://www.statskingdom.com/10StandardDeviation.html
11. ### ANOVA - 1 dependent Variable - 3 category variables

Hi JDB I assume you mean one category variable with 3 values? say, 3 groups? It means that the standard deviations of all the groups are equal. You may check it using the Levene's test. The normal assumption is not important for a large sample size. (usually, the averages will distribute...
12. ### t, Z, and s; known vs estimated sigma

Hi Fed, Even if R put the line on df=1000, you may decide to put the line on 5000. It is probably related to the precision level and performance, If I remember correctly R distributions give the precision of 7 digits. So if df=121 will give a precision level of 7 digits, and the calculation is...
13. ### Minimum population size for statistical tests?

Generally, you use statistical tests when you can't use the full population data, and you take only a sample of the data, trying to understand if the sample's results represent the population. But I think that some times it is okay to use statistics also on the full population. If the full...
14. ### Difference between t-test and one way ANOVA

Great, PS both distributions T and F are based on the normal population, so this is not a surprising result.
15. ### t, Z, and s; known vs estimated sigma

Hi Joe, When you don't know the standard deviation you should use the t-test which uses the sample standard deviation. The t distribution has heavier tails to compensate for the inaccurate sample standard deviation. A long time ago when people didn't have computers we used tables instead of a...