In this task, you will use SUDAAN to calculate
a t-statistic and assess whether the mean systolic blood pressures (*SBP*)
in males and females age 20 years and older are statistically
different.

Follow the steps in the summary table below to produce the mean SBP using the SUDAAN procedure *proc descript*.

IMPORTANT NOTE

These programs use variable formats listed in the Tutorial Formats page. You may need to format the variables in your dataset the same way to reproduce results presented in the tutorial.

Statements | Explanation |
---|---|

data =analysis_data; by sdmvstra sdmvpsu; ; |
Use the SUDAAN procedure, |

data=analysis_data design=wr; |
Use the |

nest sdmvstra sdmvpsu; |
Use the |

weight wtmec4yr; |
Use the |

subpopn ridageyr >= 20 ; |
Use the Because only those 20 years and older are of interest in
this example, use
the |

class riagendr/NoFREQ; |
Use a |

var bpxsar; |
Use the |

print nsum mean semean/style=nchs; &nbp; |
Use the |

rformat riagendr sexfmt. ; |
Use the |

rtitle
"Mean
systolic blood pressure: NHANES 1999-2002"
; |
Use the |

- 9,056 respondents had information on
systolic blood pressure (
*SBP*). - The results indicate the mean
*SBP*was 124 for males and 122 for females.

A t-test is used to test whether the mean SBP between males and females obtained in the previous step is statistically significant different.

Request the t-test from the SUDAAN procedure *proc descript* and
follow the steps in the summary table below.

IMPORTANT NOTE

Note that this program and the previous program to
produce means in Step 1 are identical up to the *var
*statement.

IMPORTANT NOTE

Statements | Explanation |
---|---|

data =analysis_data; by sdmvstra sdmvpsu; ; |
Use the SUDAAN procedure, |

data=analysis_data design=wr; |
Use the |

nest sdmvstra sdmvpsu; |
Use the |

weight wtmec4yr; |
Use the |

subpopn ridageyr >= 20 ; |
Use the Because only those 20 years and older are of interest in
this example, use
the |

class riagendr/NoFREQ; |
Use a |

var bpxsar; |
Use the |

contrast riagendr = ( 1 - 1 )/name = "Males vs. Females" ; |
Use the |

print nsum t_mean p_mean/style=nchs; |
Use the |

rformat riagendr sexfmt. ; |
Use the |

rtitle "Significance test for difference between mean systolic blood pressure for males and females" ; rtitle2 "NHANES 1999-2002" ; |
Use the |

- 9,056 respondents had information on systolic blood pressure where the degrees of freedom was 29.
- To test the hypothesis that the difference between the two means is zero, the t-statistic with 29 degrees of freedom is computed as 2.64. The p-value is 0.0132, which indicates that the probability of obtaining a value of the t-statistic whose absolute value is greater than or equal to 2.64 is 0.0132.
- Therefore, the null hypothesis is rejected at the 0.05 level.