Questions tagged [interquartile]
The interquartile range or midspread is a central interval containing 50% of the data, eliminating the 25% smallest and 25% largest observations.
7
questions
36
votes
3
answers
69k
views
Outlier Detection on skewed Distributions
Under a classical definition of an outlier as a data point outide the 1.5* IQR from the upper or lower quartile, there is an assumption of a non-skewed distribution. For skewed distributions (...
- 361
12
votes
2
answers
971
views
Why is the Tukey's IQR not used in the R program?
I was writing an R Markdown for calculating measures of spread and was surprised to find that the IQR function does not use the IQR calculation I am used to using, ...
- 13.7k
14
votes
1
answer
7k
views
Why is the 95% CI for the median supposed to be $±1.57*IQR/\sqrt{N}$?
In various sources (see e.g. here), the following formula is given for confidence interval for median (especially for the purpose of drawing notches on box-and-whisker plots):
$$
95\%\ CI_{\rm median}...
- 425
4
votes
2
answers
16k
views
What does the IQR/median mean?
What does IQR/Med tell you about the data? What is the purpose of dividing the IQR by the Median?
Examples:
...
- 43
4
votes
1
answer
20k
views
Negative inner fence. How can you find the outlier using 1.5 x IQR?
I'm trying to find outliers using 1.5 x interquartile range but I'm getting a negative value for the lower bound. I found Q3 and Q1 which are 13.30 & 3.00 respectively but for the lower bound i ...
- 41
2
votes
1
answer
613
views
Estimating Quartiles with Moments
The Wikipedia article on Skewness indicates that the median of a distribution can be estimated from the mean, standard deviation, and skeweness with an error term that goes as $O(skewness^2)$. ...
- 375
2
votes
3
answers
5k
views
Find Q1 and Q3 from median and IQR
A study gives the following:
$n = 67$
mean = 73
sd = 68
median = 55
IQR = 66
Is it possible from this information to get the actual Q1 and Q3 values? I used the $n$, mean & sd to get 95% ...
- 21