#### Question

Find the mean and variance for the following frequency distribution.

Classes |
0-30 |
30-60 |
60-90 |
90-120 |
120-150 |
150-180 |
180-210 |

Frequencies |
2 |
3 |
5 |
10 |
3 |
5 |
2 |

#### Solution

Class |
Frequency f_{i} |
Mid-point x_{i} |
`y_i = (X_i-105)/30` | y_{i}^{2} |
f_{i}y_{i} |
f_{i}y_{i}^{2} |

0-30 |
2 |
15 |
–3 |
9 |
–6 |
18 |

30-60 |
3 |
45 |
–2 |
4 |
–6 |
12 |

60-90 |
5 |
75 |
–1 |
1 |
–5 |
5 |

90-120 |
10 |
105 |
0 |
0 |
0 |
0 |

120-150 |
3 |
135 |
1 |
1 |
3 |
3 |

150-180 |
5 |
165 |
2 |
4 |
10 |
20 |

180-210 |
2 |
195 |
3 |
9 |
6 |
18 |

30 |
2 |
76 |

Is there an error in this question or solution?

Solution Find the Mean and Variance for the Following Frequency Distribution. 0-30 30-60 60-90 90-120 120-150 150-180 180-210 Concept: Variance and Standard Deviation - Standard Deviation of a Discrete Frequency Distribution.