Applet for calculating heritability for threshold traits (diseases)

8.3 Applet for calculating heritability for threshold traits (diseases)

The calculations are based on disease frequencies in the general population (Population) and among relatives (Indiv. related ) to diseased animals. The relatives can be (both parents diseased) first degree (father, mother or full sibs) or second degree (half sibs, grand parents).

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Observe: The chi-square test calculation is based on: that the related ones is subtracted from the population numbers!

Example:
Enter your observed numbers and degree of relationship (green fields) and then press the Calculate button. The values in the (Degree of relationship) field should 1, .5 and .25 for the three above mentioned cases.
You can also enter the frequencies (yellow fields) but then the numbers shall be zeros in the observed number fields. Results are rounded to four decimals.
Illustration of the case where both parents are affected are given below. The applet is initiated with the actual data; to see the calculations press the Calculate button.

Questions:
In the table below is given observed numbers for disease frequencies in the population and in first-degree relatives to diseased animals. 
              Normal  Diseased  Frequency
------------------------------------------
Population      980       20        0.020
First-degree
relative        140       10        0.066
------------------------------------------

Estimate the heritability.
What is the relative risk to be related to a diseased animal ?
Is the heritability statistically significant different from 0 with (p< 0.05) ?

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