Embed Code - If you would like this activity on your web page, copy the script below and paste it into your web page.

Normal Size Small Size show me how

Normal Size Small Size show me how

# 1Cate vs 1 Quantit

### data analysis

Question | Answer |
---|---|

useful graphs | comparative boxplot or comparative histogram |

useful numbers | mean and standard deviation for each group |

formula for mean | x ̅=1/N ∑_((i=1))^N▒xi preferable for approximately normal data |

formula for standard deviation | s=√(1/(N-1) ∑_(i=1)^N▒〖(xi-x)〗^2 ) preferable for approximately normal data |

an outlier is | more than 1.5 x IQR lower than Q1 more than 1.5 x IQR higher than Q3 |

linear transformation | transformation of a variable from x to xnew |

examples of linear transformation use | change of units use of normal assumption therefore to find 'z' scores |

formula for linear transformation | xnew=a+bx |

formula for mean after linear transformation | xnew=a+bx |

formula for standard deviation after linear transformation | snew=bs |

density curves | area under the curve in any range of values is the proportion of all observations that fall within that range for a quantitative variable = like a smoothed out histogram describes probabilistic behaviour |

total area under a density curve equals? | 1 |

normality assumption | normal curve can be used if a histogram looks like a normal curve termed 'reasonable' must start at 0 and end at 0 |

normal quantile plot | if in a straight line, or close to it, then normal and assumption is reasonable |

68-95-99.7% rule | 68% of results will be within 1 standard deviation of the mean 95% of results will be within 2 standard deviations of the mean 99.7% of data will be within 3 standard deviations of the mean |

symbol for mean of a density curve | μ |

symbol for the standard deviation of a density curve | σ |

normal distribution short hand | X = random variable N = normal distribution first number in brackets = mean second number in brackets = standard deviation |

standard normal variable | Z corresponds to the area under the curve of the corresponding region will always be to the left |

standard normal distribution table | to find P: Z found along x and y axis to find Z: P found in table ordered from smallest to largest |

reverse standard normal distribution table | P(Z<c) c = right of Z |

X is | N(μ,σ) |

standardising transformation | Z= (X-μ)/σ used when distribution is N(0,1)(is normal but needs proportions changed) |

Created by:
Nymphette