Question

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
egative\ 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 samples	positive result	negative result
does not contain organic matter	300		240

if a soil sample test gives a positive result, it is
% likely that the soil sample contains organic matter.

Explanation:

Step1: Calculate negative results for organic matter

For samples with organic matter, positive results are 665, total samples with organic matter are 700. So negative results = \( 700 - 665 = 35 \).

Step2: Calculate positive results for no organic matter

For samples without organic matter, total samples are 300, negative results are 240. So positive results = \( 300 - 240 = 60 \).

Step3: Calculate total positive results

Total positive results = positive with organic + positive without = \( 665 + 60 = 725 \).

Step4: Calculate probability

Probability = \( \frac{\text{Positive with organic}}{\text{Total positive}} = \frac{665}{725} \approx 0.917 \), so percentage is \( 0.917 \times 100 \approx 91.7\% \).

First, fill the table:

• "Negative Result" for "Contains Organic Matter": 35
• "Positive Result" for "Does Not Contain Organic Matter": 60

Then, the probability percentage:

Answer:

Table fill: 35 (for negative in organic), 60 (for positive in non - organic)
Probability percentage: 91.7