Quick Answer: What Do Points Above And Below The Whiskers Represent In A Box Plot?

What do whiskers represent in a box plot?

In a box and whisker plot: the ends of the box are the upper and lower quartiles, so the box spans the interquartile range.

the median is marked by a vertical line inside the box.

the whiskers are the two lines outside the box that extend to the highest and lowest observations..

What is the lower and upper extreme in a box and whisker plot?

A box-and-whisker plot or box plot is a graph that represents the distribution of a data set. … Lower and upper quartiles – values that divide the data set into four sections. Lower and upper extremes – the smallest and largest values in the data set.

How do you interpret outliers in a box plot?

When reviewing a box plot, an outlier is defined as a data point that is located outside the whiskers of the box plot. For example, outside 1.5 times the interquartile range above the upper quartile and below the lower quartile (Q1 – 1.5 * IQR or Q3 + 1.5 * IQR).

How do you find the minimum in a box and whisker plot?

At the ends of the box, you” find the first quartile (the 25% mark) and the third quartile (the 75% mark). The far left of the chart (at the end of the left “whisker”) is the minimum (the smallest number in the set) and the far right is the maximum (the largest number in the set).

What does a positively skewed box plot mean?

Positively Skewed : For a distribution that is positively skewed, the box plot will show the median closer to the lower or bottom quartile. A distribution is considered “Positively Skewed” when mean > median. It means the data constitute higher frequency of high valued scores.

How do you calculate upper and lower whiskers?

If there are individual data points plotted, the whiskers indicate the largest/lowest points inside the range defined by 1st or 3rd quartile plus 1.5 times IQR.

How do you interpret box plots?

Definitions. The median (middle quartile) marks the mid-point of the data and is shown by the line that divides the box into two parts. 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.

What does Range mean in a box and whisker plot?

Box-and-Whisker Plots: Finding the Range and Mid-Range in a Series of Numbers. Video Grade: 6. Range is the difference between the largest and smallest numbers; and midrange is the average of the largest and smallest number. Practice with this problem.

Why is a box plot better than a histogram?

Histograms and box plots are very similar in that they both help to visualize and describe numeric data. Although histograms are better in determining the underlying distribution of the data, box plots allow you to compare multiple data sets better than histograms as they are less detailed and take up less space.

How do you compare two box plots?

Guidelines for comparing boxplotsCompare 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.

Why would a box plot not have a whisker on one side?

A simpler formulation is this: no whisker will be visible if the lower quartile is equal to the minimum, or if the upper quartile is equal to the maximum.

How do you find q1 and q3?

Q1 is the median (the middle) of the lower half of the data, and Q3 is the median (the middle) of the upper half of the data. (3, 5, 7, 8, 9), | (11, 15, 16, 20, 21). Q1 = 7 and Q3 = 16. Step 5: Subtract Q1 from Q3.