Linked Questions

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1answer
930 views

T-test or Mann-Whitney U test [duplicate]

Given the central limit theorem, can you always use a t-test to test a difference between two groups even if the data are not normally distributed but the sample size is large enough? Stated in ...
1
vote
1answer
46 views

Is it safe to use one sample-t test with a dataset of size 5000 while the population distribution is not normal? [duplicate]

I have a random variable X, number of hours that kids from 10-12 years old spend on video games in one month in a specific country, and I want to test the hypothesis that the mean of my population $...
14
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2answers
6k views

Independent samples t-test: Do data really need to be normally distributed for large sample sizes?

Let's say I want to test if two independent samples have different means. I know the underlying distribution is not normal. If I understand correctly, my test statistic is the mean, and for large ...
12
votes
1answer
2k views

Is bootstrapping appropriate for this continuous data?

I'm a complete newbie :) I'm doing a study with a sample size of 10,000 from a population of about 745,000. Each sample represents a "percentage similarity". The great majority of the samples are ...
3
votes
3answers
11k views

Repeated measures ANOVA or Friedman test?

I have a study with 35 subjects who received hypercoagulability testing at 4 different times (before surgery, after, at 1 week, and at 1 month). Each subject has 9 different test of hyper ...
2
votes
1answer
2k views

Is having too high variance a problem when doing t-test

I am comparing scores of two student groups using t-test (in scikit-learn). Each group has different number of students. Since there are considerable numbers of 0 scores in my data, the standard ...
2
votes
1answer
3k views

Do statistical tests require a normal distribution in the sample or in the population?

Certaint tests, such as the t-test, require a normal distribution. Yet I have never quite understood what exactly has to be normally distributed. Let's use age as an example. Age is rarely normally ...
3
votes
3answers
625 views

If the parent distribution is skewed, but the sample size is greater than 30, is the distribution of the sample mean nearly Normal?

I have my AP Stats exam tomorrow and had this question. I apologize if it is too simplistic for this forum. I'm pretty sure the sample's distribution is nearly normal, but not 100%, can someone ...
1
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0answers
2k views

R: Shapiro-Wilk test for log-normal distribution

I would like to use a t-test for hypothesis testing on the amount of calories consumed by women per day. The distribution of this variable is right-skewed and a log-transformation increase its ...
5
votes
2answers
198 views

Related to exponential distribution

I am a beginner in statistics.(and probability theory too).I studied Exponential distribution and just started doing problems when I got stuck in the following one: Suppose that $X_1, . . . , X_n$ ...
3
votes
1answer
585 views

Can we ALWAYS assume normal distribution if n >30?

I'm in a debate with a coworker and I'm starting to wonder if I'm wrong but the internet is confusing me more. We have continuous data [0,infinity) that is retrospectively selected on individuals. The ...
1
vote
1answer
932 views

Big sample size (n>50.000), but still highly skewed. Is central limit theorem still valid?

I have 12 samples with approx. 50.000 data points each. I got it from a content analysis of Reddit comments. The data is generated by analyzing the comments with LIWC tool and it gives me information ...
2
votes
1answer
970 views

Statistic on non-normalized data

Not that strong in statistics, so I need a little help getting started with some data I've gathered. In my experiment subjects had to perform tasks while I took time for them to complete it. Now, I ...
0
votes
1answer
450 views

Are 25 sample means, each of size 5, approximately normally distributed?

If I draw five simple random sample observations from a non-normal population, calculate their mean, and repeat 24 more times, will the 25 means I've computed approximate a normal distribution? The ...
3
votes
2answers
152 views

Determine which performance intervention is best?

Suppose I have numerical data describing the total process time for a given software simulation. This data is broken up into 5 groups (Base, AD1, AD2, AD3, AD4) each detailing a different performance ...

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