# AP Statistics Curriculum 2007 EDA Freq

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* A '''frequency distribution''' is a display of the number (frequency) of occurrences of each value in a data set. | * A '''frequency distribution''' is a display of the number (frequency) of occurrences of each value in a data set. | ||

* A '''relative frequency''' distribution is a display of the percent (ratio or frequency to sample-size) of occurrences of each value in a data set. | * A '''relative frequency''' distribution is a display of the percent (ratio or frequency to sample-size) of occurrences of each value in a data set. | ||

+ | * A [http://en.wikipedia.org/wiki/Percentile percentile] is the <u>value</u> of a variable that devides the real line into two segments - the left one caontaining certain percent (say 13%) of the observations for the specific process, and the righ interval containing the complement peecent of observations (in this case 87%). The 30<sup>th</sup> percentile is the value (measurement) that abounds above 30% and below 70% of the observations from a process. | ||

+ | * The (three) '''quartiles''' are the special cases of percentiles for Q<sub>1</sub>=25%, Q<sub>2</sub>=50% (median) and Q<sub>3</sub>=75%. | ||

===Example=== | ===Example=== |

## Revision as of 21:34, 6 March 2008

## Contents |

## General Advance-Placement (AP) Statistics Curriculum - Summarizing data with Frequency Tables

### Summarizing data with Frequency Tables & Histograms

There are two ways to describe a data set (sample from a population) - Pictorial Graphs or Tables of Numbers. Both are important for analyzing data.

### Definitions

- A
**frequency distribution**is a display of the number (frequency) of occurrences of each value in a data set. - A
**relative frequency**distribution is a display of the percent (ratio or frequency to sample-size) of occurrences of each value in a data set. - A percentile is the
__value__of a variable that devides the real line into two segments - the left one caontaining certain percent (say 13%) of the observations for the specific process, and the righ interval containing the complement peecent of observations (in this case 87%). The 30^{th}percentile is the value (measurement) that abounds above 30% and below 70% of the observations from a process. - The (three)
**quartiles**are the special cases of percentiles for Q_{1}=25%, Q_{2}=50% (median) and Q_{3}=75%.

### Example

The table below shows the stage of disease at diagnosis of breast cancer in a random sample of 2092 US women.

Stage | Frequency | Relative Frequency |
---|---|---|

0 | 197 | 0.09 |

I | 691 | 0.33 |

II | 703 | 0.34 |

III | 314 | 0.15 |

IV | 187 | 0.09 |

Total | 2092 | 1.00 |

### Computational Resources: Internet-based SOCR Tools

- SOCR Charts allows you to generate graphical representations (including frequency histograms) of a variety of datasets.
- The SOCR Charts activities provide usage-instructions, examples and demonstrations of how to use SOCR Charts.

### Hands-on activities

You can copy and paste the first 2 columns in the data table above in the SOCR Charts (BarChart --> XYPlot --> HistogramDemo7). You can see this SOCR Charts activity for help with histogram plots.

- The graph below illustrates the (raw) frequency histogram (using counts)

- The graph below show the relative frequency histogram (using the last column of the table above).

### References

- SOCR Home page: http://www.socr.ucla.edu

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