Linked Questions

107
votes
16answers
10k views

What misused statistical terms are worth correcting?

Statistics is everywhere; common usage of statistical terms is, however, often unclear. The terms probability and odds are used interchangeable in lay English despite their well-defined and different ...
41
votes
3answers
14k views

Which has the heavier tail, lognormal or gamma?

(This is based on a question that just came to me via email; I've added some context from a previous brief conversation with the same person.) Last year I was told that the gamma distribution is ...
31
votes
6answers
3k views

Can somebody offer an example of a unimodal distribution which has a skewness of zero but which is not symmetrical?

In May 2010 Wikipedia user Mcorazao added a sentence to the skewness article that "A zero value indicates that the values are relatively evenly distributed on both sides of the mean, typically but not ...
12
votes
5answers
10k views

How is the kurtosis of a distribution related to the geometry of the density function?

The kurtosis is to measure the peakedness and flatness of a distribution. The density function of the distribution, if it exists, can be viewed as a curve, and has geometric features (such as ...
8
votes
4answers
583 views

Kurtosis of made up distribution

Take a look at the image below. Blue line indicates standard normal pdf. The red zone is supposed to be equal to the sum of grey areas (sorry for awful drawing). I wonder can we create a new ...
8
votes
2answers
1k views

Skewness, kurtosis and how many standard deviations values are from the mean

As is well known for the normal distribution, 68% of the probability mass is within one standard deviation of the mean, 95% within two standard deviations and 99.7% within 3 standard deviations. ...
5
votes
2answers
614 views

Testing for normality in non-normal distributions with zero skewness and zero excess kurtosis

[This question was formerly called "On Non-normal distributions with zero skewness and zero excess kurtosis" and relabeled to better reflect its focus.] I am trying to write a little simulation using ...
1
vote
1answer
617 views

Question about Normality of 5-point Likert scale

I'm really having a hard time trying to normalize my data. My study is about green IT product acceptance. There are eight factors, six are 5-point Likert scale (Str.disagree - Str.agree), one is 2-...
2
votes
1answer
715 views

Similarity measures between bimodal distributions

I have to compare two bimodal distributions. So far, I have found the Bimodality Coefficient: $$ BC = \frac{\mu_{3}^{2} + 1}{\mu_{4} + 3\frac{(n-1)^2}{(n-2)(n-3)}}, $$ with $\mu_{3}$ referring to ...
0
votes
2answers
63 views

Is there any statistic or method which could describe how much a distribution deviates from the normal distribution?

Is there any statistic or method which could describe how much a distribution deviates from the normal distribution? I want to test if my data is normal or not at some level of significance, and I ...
1
vote
1answer
40 views

How can I test normality of data incrementally?

I plan to track the mean and variance of a data set as it grows over time, but I can't keep the actual data, just the current mean and variance. Later, I want to estimate the probability of a given ...