**Table 3. Analysis of variance of regression coefficient calculated for gelatin extraction from Korean native black goat skin**

Independent variable | Extraction yield (%) | Gel strength (g) |

Regression coefficient | p-value | Regression coefficient | p-value |

Constant | 12.561 | <0.001 | 263.14 | <0.001 |

Linear | | | | |

X_{1} | 1.777 | <0.001 | –6.10 | 0.002 |

X_{2} | 0.501 | 0.004 | –2.34 | 0.110 |

Quadratic | | | | |

X_{1}^{2} | –0.697 | 0.005 | 0.55 | 0.780 |

X_{2}^{2} | 0.036 | 0.845 | –4.65 | 0.043 |

Interaction | | | | |

X_{1}X_{2} | –0.117 | 0.450 | –1.59 | 0.346 |

X_{1}, extraction temperature (°C); X_{2}, extraction time (h).