A box and whisker plot is based on the *minimum and maximum values*, the *upper and lower quartiles* and the *median*. This type of plot provides a good way to compare two or more samples.

Note: Box and whisker plots must always be drawn accurately to scale.

Given the information below, draw a box and whisker plot.

Minimum | 82 |

Lower quartile | 94 |

Median | 95 |

Upper quartile | 102 |

Maximum | 110 |

The box and whisker plot is shown below.

Draw a box and whisker plot for this sample:

5 | 7 | 1 | 9 | 11 | 22 | 15 |

First list the sample in order, to determine the median and the quartiles.

The box and whisker plot is shown below:

A gardener collected data on two types of tomato. The box and whisker plot below shows data for the masses in grams of the tomatoes in the two samples.

Compare and contrast the two types and advise the gardener which type of tomato he should grow in future.

Type A | Type B | |

Median | 52 grams | 52 grams |

Lower Quartile | 49 grams | 51 grams |

Upper Quartile | 57 grams | 54 grams |

Range | 14 grams | 8 grams |

Interquartile Range | 8 grams | 3 grams |

From this table we can see that both types of tomato have the same average mass because their medians are the same.

Comparing the medians and interquartile ranges shows that there is far more variation in the masses of the type A tomatoes, which means that the masses of type B are more consistent than those of type A.

However, comparing the two box and whisker plots, and the upper quartiles, shows that type A tomatoes will generally have a larger mass than those of type B.

Nevertheless, there will be some type A tomatoes that are lighter than any of type B.

Taking all this together, the gardener would be best advised to plant type A tomatoes in future as he is likely to get a better yield from them than from type B.