Hot to calculate these type of probability

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raymond

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For these type of question, I see that some online resources construct a table to solve it, but I don’t know how to fill the rest of data40C6C145-6420-4FC2-8DB3-461997ED200A.jpeg
 
You have (a) and (b) correct. For (c) what is the definition of "sensitivity" of a test?
 
Where did you get the 0.16 you put in the table? That would imply that 40% of the population have the gene.
 
But that would imply that 100% of the population have the gene! It should be 25%.

I wonder if you are using the table differently than it is intended.
 
Dr.Peterson said:
But that would imply that 100% of the population have the gene! It should be 25%.

I wonder if you are using the table differently than it is intended.
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I just conduct it by the given data. Maybe the table is wrong. Actually, I have no idea in this question
 
Can you show me an example of that type of table, filled in fully, from an example you have been given? I need to know what you have been taught about it, which could be different from what I would mean by it.

What I expect of the table is that each entry shows the percent of the entire population that meet the criterion. The top left entry is the percent who have the gene and test positive. The lower left entry should be the percent who have the gene and test negative, not the percent who do not both have the gene and test negative.

The sum of all entries should be 100%; any one column should not total 100%.

Is that different from what you have been taught about such a table?
 
Dr.Peterson said:
Can you show me an example of that type of table, filled in fully, from an example you have been given? I need to know what you have been taught about it, which could be different from what I would mean by it.

What I expect of the table is that each entry shows the percent of the entire population that meet the criterion. The top left entry is the percent who have the gene and test positive. The lower left entry should be the percent who have the gene and test negative, not the percent who do not both have the gene and test negative.

The sum of all entries should be 100%; any one column should not total 100%.

Is that different from what you have been taught about such a table?
Click to expand...
In my course, it has mentioned an example like the below image. And your explaining is correct
92F763EA-2214-4566-A333-4CA112F83B37.jpeg
 
Thanks.

Do you see that (although this example uses actual counts rather than percentages) the total of each column is the number that fit the heading of the column, and the total of all the numbers is the total number of people?

So do you see that it is wrong in your problem for the first column to be 0.24 + 0.76, which adds up to 1.00 (100%)?

What should the sum of that column really be? Finish your table, and answer the question, so we can discuss it further.
 
Dr.Peterson said:
Thanks.

Do you see that (although this example uses actual counts rather than percentages) the total of each column is the number that fit the heading of the column, and the total of all the numbers is the total number of people?

So do you see that it is wrong in your problem for the first column to be 0.24 + 0.76, which adds up to 1.00 (100%)?

What should the sum of that column really be? Finish your table, and answer the question, so we can discuss it further.
Click to expand...
Is it the sum of column should be the percentage of the people who have HPQ gene?
 
So, what is the rest of the table, and what answers do you get for parts (c) and (d)? Please do as much as you can rather than wait for a response after each tiny step, to avoid wasting time. We can make faster progress if you are bold.
 
Dr.Peterson said:
So, what is the rest of the table, and what answers do you get for parts (c) and (d)? Please do as much as you can rather than wait for a response after each tiny step, to avoid wasting time. We can make faster progress if you are bold.
Click to expand...
Should it be in this way?3713884D-BAE8-4DF8-8EB9-D93C45C30284.jpeg
 
Beautiful!

So the test detects 96% of people with the gene; but only 80% of those who test positive actually have the gene.
 
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