I sent my question as an attachment!

1. The baseline prevalence of breast cancer is:

= 0.12%.

Interpretation: 0.12% of the starting population was diagnosed with breast cancer.

2. The one-year cumulative incidence (incidence proportion) for each of the three years:

Time         Starting        Breast        Lost to      Cumulative

             Population     Cancer     Follow-up     Incidence

Start        20,000            24                0            

1980         19,976            50             80                 0.25%

1981          19,846            64               6                 0.32%

1982         19,776            48              10                 0.24%

End           19,718                

Explanation:

a) Data and Calculations:

Baseline starting population = 20,000

Breast Cancer diagnosis at the starting period = 24

Baseline prevalence = 24/20,000 = 0.12%

Time         Starting        Breast        Lost to

             Population     Cancer     Follow-up

Start        20,000            24                0

1980         19,976            50             80

1981                                 64               6

1982                                48              10

End                  

Time         Starting        Breast        Lost to      Cumulative

             Population     Cancer     Follow-up     Incidence

Start        20,000            24                0            

1980         19,976            50             80                 0.25% (50/19,976 * 100)

1981          19,846            64               6                 0.32% (64/19,846 * 100)

1982         19,776            48              10                 0.24% (48/19,776 * 100)

End           19,718                

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