Type the correct answer in each box. Use numerals instead of words. A new test is developed to test for organic matter in soil samples, giving "positive" or "negative" results to indicate that a sample does or does
not contain organic matter.
For a soil sample that contains organic matter, the test will give a positive result 95% of the time and a negative result (false negative) 5% of the
time. For a soil sample that does not contain organic matter, the test will give a positive result (false positive) 20% of the time and a negative
result 80% of the time.
A study included a population of 1,000 soil samples, and 70% of those studied where known to contain organic matter.
Fill in the missing values in the table and statement below. If necessary, round the percentage to one decimal place.
Number of Positive Negative
Samples
Result
Result
Contains
700
665
Organic Matter
Does Not
Contain
300
240
Organic Matter
If a soil sample test gives a positive result, it is
% likely that the soil sample contains organic matter.