## Reference Notes

Unit: Statistics | Economics

Frequency Curve

Graphs of Frequency Distribution

Management: Class 11

**Frequency Curve**

If we join the vertices of the frequency polygon by freehand, then the curve so drawn is called frequency curve. It is a smooth and regular curve without any sharp turns. The area under the frequency curve, frequency polygon and histogram should be equal. It should be carefully drawn.

**Example:**

Marks | 5 – 10 | 10 – 15 | 15 – 20 | 20 – 25 | 25 – 30 |

No. of students | 2 | 5 | 4 | 8 | 3 |

**Ogive or cumulative frequency curve:**

There are two types of cumulative frequency curves.

**a) “Less than” cumulative frequency curve:** these curves are drawn by using the “less than” values of the variable and their corresponding frequencies in “less than” cumulative distribution of data.

**Example:**

Draw the “less than” frequency curve of the following data:

Price of shares (Rs.) | 50 – 100 | 100 – 150 | 150 – 200 | 200 – 250 | 250 – 300 | 300 – 350 |

No. of shares | 15 | 20 | 22 | 21 | 10 | 5 |

**Solution:**

Converting the data into “less than” frequency

Price of share (Rs.) | Cumulative frequency |

Less than 100 | 15 |

Less than 150 | 35 |

Less than 200 | 57 |

Less than 250 | 78 |

Less than 300 | 88 |

Less than 350 | 93 |

**b) “More than” cumulative frequency curve:** These curves are drawn by using the more than values of the variables and their corresponding frequencies in “more than” cumulative distribution of data.

**Example:**

“More than” frequency of the above share data is

Price of share (Rs.) | Cumulative frequency |

More than 50 | 93 |

More than 100 | 78 |

More than 150 | 58 |

More than 200 | 36 |

More than 250 | 15 |

More than 300 | 5 |