How do you interpret a Boxplot?
Half the scores are greater than or equal to this value and half are less. The middle “box” represents the middle 50% of scores for the group. The range of scores from lower to upper quartile is referred to as the inter-quartile range. The middle 50% of scores fall within the inter-quartile range.
How do you compare data in a box plot?
Guidelines for comparing boxplots
- Compare the respective medians, to compare location.
- Compare the interquartile ranges (that is, the box lengths), to compare dispersion.
- Look at the overall spread as shown by the adjacent values.
- Look for signs of skewness.
- Look for potential outliers.
What is Q3 on a box plot?
Q3 – quartile 3, the median of the upper half of the data set. IQR – interquartile range, the difference from Q3 to Q1. Extreme Values – the smallest and largest values in a data set.
How do you interpret the median and interquartile range?
There are 5 values below the median (lower half), the middle value is 64 which is the first quartile. There are 5 values above the median (upper half), the middle value is 77 which is the third quartile. The interquartile range is 77 – 64 = 13; the interquartile range is the range of the middle 50% of the data.
What do outliers show in box plots?
Both outlier and quantile box plots show the median, 25th and 75th percentiles. The 25th percentile is also the 25th quantile, which means that 25% of the data is lower than the 25th quantile. A quantile box plot adds the 2.5th, 10th, 90th and 97.5th quantiles to the outlier box plot.
How do you read quartiles?
First quartile: the lowest 25% of numbers. Second quartile: between 0% and 50% (up to the median) Third quartile: 0% to 75% Fourth quartile: the highest 25% of numbers.
What does the interquartile range represent in a box plot?
The interquartile range (IQR) is the box plot showing the middle 50% of scores and can be calculated by subtracting the lower quartile from the upper quartile (e.g. Q3−Q1).
How do you interpret Q1?
Q1. Quartiles are the three values–the first quartile at 25% (Q1), the second quartile at 50% (Q2 or median), and the third quartile at 75% (Q3)–that divide a sample of ordered data into four equal parts. The first quartile is the 25th percentile and indicates that 25% of the data are less than or equal to this value.
How do you interpret IQR and median?
Is a lower or higher IQR better?
The interquartile range (IQR) is the difference between the upper (Q3) and lower (Q1) quartiles, and describes the middle 50% of values when ordered from lowest to highest. The IQR is often seen as a better measure of spread than the range as it is not affected by outliers.