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Projection of an overpayment from an audit.

A system of accounts that can be thought of as partitioned into four areas A - D is to be audited for payment error.    A stratified sample plan is used having four strata:  A,B, C and D.

Simple random samples are drawn from each of the four strata.

In analysis of the samples, the reviewers  notice that strata A and C results are much more interesting.  Higher error rate and more serious problems.  Management asks the statistician if the extrapolation or projection can be done just on the high error rate accounts: A and C.

(*) Generally, it is not good to change the plan in the middle of the work.

 The statistician responds that "Yes, that can be done since they(A and C)  are independent random samples and so the problem can be treated as a two strata situation and the usual formulas for estimation of a total such as in Ott's text applied in the same way as would have been for the four strata case."  The other two sample results from B and D can be collected or corrected ( the over / underpayments in the samples) as "actuals" i.e. no extrapolation.

Aside from the observation (*), I don't see anything wrong with this. I don't particularly feel comfortable with this but have no "proof" that something is wrong.  By "this" I mean planning one thing and then changing it somewhat.    I would appreciate any observations or comments. 

I am never completely sure the right way to post something on this ASA site so if I am doing it the wrong way please let me know.  Thanks again,

Greg Dobbins

Projection of an overpayment from an audit.

A system of accounts that can be thought of as partitioned into four areas A - D is to be audited for payment error.    A stratified sample plan is used having four strata:  A,B, C and D.

Simple random samples are drawn from each of the four strata.

In analysis of the samples, the reviewers  notice that strata A and C results are much more interesting.  Higher error rate and more serious problems.  Management asks the statistician if the extrapolation or projection can be done just on the high error rate accounts: A and C.

(*) Generally, it is not good to change the plan in the middle of the work.

 The statistician responds that "Yes, that can be done since they(A and C)  are independent random samples and so the problem can be treated as a two strata situation and the usual formulas for estimation of a total such as in Ott's text applied in the same way as would have been for the four strata case."  The other two sample results from B and D can be collected or corrected ( the over / underpayments in the samples) as "actuals" i.e. no extrapolation.

Aside from the observation (*), I don't see anything wrong with this. I don't particularly feel comfortable with this but have no "proof" that something is wrong.  By "this" I mean planning one thing and then changing it somewhat.    I would appreciate any observations or comments. 

I am never completely sure the right way to post something on this ASA site so if I am doing it the wrong way please let me know.  Thanks again,

Greg Dobbins

Projection of an overpayment from an audit.

A system of accounts that can be thought of as partitioned into four areas A - D is to be audited for payment error.    A stratified sample plan is used having four strata:  A,B, C and D.

Simple random samples are drawn from each of the four strata.

In analysis of the samples, the reviewers  notice that strata A and C results are much more interesting.  Higher error rate and more serious problems.  Management asks the statistician if the extrapolation or projection can be done just on the high error rate accounts: A and C.

(*) Generally, it is not good to change the plan in the middle of the work.

 The statistician responds that "Yes, that can be done since they(A and C)  are independent random samples and so the problem can be treated as a two strata situation and the usual formulas for estimation of a total such as in Ott's text applied in the same way as would have been for the four strata case."  The other two sample results from B and D can be collected or corrected ( the over / underpayments in the samples) as "actuals" i.e. no extrapolation.

Aside from the observation (*), I don't see anything wrong with this. I don't particularly feel comfortable with this but have no "proof" that something is wrong.  By "this" I mean planning one thing and then changing it somewhat.    I would appreciate any observations or comments. 

I am never completely sure the right way to post something on this ASA site so if I am doing it the wrong way please let me know.  Thanks again,

Greg Dobbins

Projection of an overpayment from an audit.

A system of accounts that can be thought of as partitioned into four areas A - D is to be audited for payment error.    A stratified sample plan is used having four strata:  A,B, C and D.

Simple random samples are drawn from each of the four strata.

In analysis of the samples, the reviewers  notice that strata A and C results are much more interesting.  Higher error rate and more serious problems.  Management asks the statistician if the extrapolation or projection can be done just on the high error rate accounts: A and C.

(*) Generally, it is not good to change the plan in the middle of the work.

 The statistician responds that "Yes, that can be done since they(A and C)  are independent random samples and so the problem can be treated as a two strata situation and the usual formulas for estimation of a total such as in Ott's text applied in the same way as would have been for the four strata case."  The other two sample results from B and D can be collected or corrected ( the over / underpayments in the samples) as "actuals" i.e. no extrapolation.

Aside from the observation (*), I don't see anything wrong with this. I don't particularly feel comfortable with this but have no "proof" that something is wrong.  By "this" I mean planning one thing and then changing it somewhat.    I would appreciate any observations or comments. 

I am never completely sure the right way to post something on this ASA site so if I am doing it the wrong way please let me know.  Thanks again,

Greg Dobbins