Linked Questions

0
votes
2answers
2k views

Best graphical representation of t-test data [duplicate]

In my paper I have a number of t-tests. I am thinking of representing some graphically. What is the best way of doing that in R?
53
votes
4answers
30k views

How are regression, the t-test, and the ANOVA all versions of the general linear model?

How are they all versions of the same basic statistical method?
19
votes
3answers
94k views

How to assess skewness from a boxplot?

How to decide skewness by looking at a boxplot built from this data: 340, 300, 520, 340, 320, 290, 260, 330 One book says, "If the lower quartile is farther from the median than the upper quartile, ...
16
votes
5answers
4k views

Checking ANOVA assumptions

A few months ago I posted a question about homoscedasticity tests in R on SO, and Ian Fellows answered that (I'll paraphrase his answer very loosely): Homoscedasticity tests are not a good tool ...
13
votes
4answers
2k views

Graphing small samples

I have a small data set of 14 separate times to complete a task. However I am having difficulty finding an appropriate graph to use to graph the data. If the sample was larger I would use a box plot ...
7
votes
4answers
18k views

One sided confidence interval for hypothesis testing

I'm having a hard time understanding how to use confidence intervals for hypothesis testing. I've seen examples to reject a null hypothesis, but don't understand how to use a one-sided confidence ...
8
votes
1answer
4k views

T-test using only summary data in a box plot

I have the 5 number summary (min, Q1, Median, Q3, max) from two boxplots and wanted to test whether or not the averages of the groups in the two boxplots were significantly different. I would like ...
6
votes
1answer
2k views

Is using error bars for means in a within-subjects study wrong?

I seem to recall one of my professors saying that error bars are completely uninformative when comparing repeated measures taken from a single group. Is that true? Surely many studies compute the ...
4
votes
2answers
1k views

Approaches for comparing visual representation of two distributions with unequal sample sizes

I have two distributions of continuous, unpaired measurements. I would like to visualize the two distributions with a pair of histograms, counting measurements that fall over a bin's interval. Are ...
6
votes
1answer
2k views

Displaying mean +/- st. error or confidence interval on bar charts

When I look at scientific papers, bar charts I usually come to see are shown with mean +/- sem (standard error of the mean). As stated here, When standard error (SE) bars do not overlap, you ...
2
votes
1answer
3k views

Can I use Standard deviation (in Excel error bars) with median in a graph?

I have a variable (vitamin D levels) that does not follow normal distribution. I wanted to plot its variation throughout a period of time. I used the median. However I wanted to add error bars in this ...
0
votes
2answers
1k views

One Way ANOVA, 3 groups with unequal sample sizes [closed]

I have a question regarding one way ANOVA in order to see whether there is a significant difference using SPSS; I have 3 groups of unequal sample sizes (n=7, n=7 and n= 13). I know that the sample ...
1
vote
2answers
92 views

Transformation of distribution before applying tests or models?

I have observations from an experiment, and each of the observations belongs to one of 2 groups (patients, controls). I would like to test for group differences in the data using a test. I would ...