**Data Sample**

# The NY Dairy Herd Improvement Cooperative in Upstate New York (NYDHIC) collects and analyzes data on milk production. One question of interest here is how to develop a suitable model to predict current milk production from a set of measured variables.

# The response variable (current milk production in pounds) and the predictor variables are given in Table below (Data Variable Definitions). Samples are taken once a month during milking. The period that a cow gives milk is called lactation. Number of lactations is the number of times a cow has calved or given milk.

# The recommended management practice is to have the cow produce milk for about 305 days and then allow a 60-day rest period before beginning the next lactation.

# The data set, consisting of 199 observations, was compiled from the NYDHI milk production records.

The Milk Production data can be found on the following Web site:

**# http://www.ats.ucla.edu/stat/stata/examples/chp/chpstata_dl.htm**

**# http://www.ats.ucla.edu/stat/examples/chp/p004.txt**

**Data Variable Definitions**

Variable |
Definition |

Current | Current month milk production in pounds |

Previous | Previous month milk production in pounds |

Fat | Percent of fat in milk |

Protein | Percent of protein in milk |

Days | Number of days since present lactation |

Lactation | Number of lactations |

I79 | Indicator variable (0 if Days < 79 and 1 if Days > 79) |