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need a study partner for MRCPsych Paper 3 revision

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Hi I live in Miltonkeynes, Buckinghamshire.

I would like to have a study partner espcecially for critical apprasial bit.

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Same here. I prepared so well apart from critical appraisal, I live in Suffolk though which is the only downside(being too far)

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Where about are you in milton keynes? i am not too far away. agree it would be better to study critical appraisal jointly. its a major let down

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Hi Guys, Why cant we do the joint study for critical appraisal here in this forum?

We can identify some topics to discuss and start doing questions around it, this is the best way of preparing stats.

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Yes it is a great idea, I think we should start critical appraisal study group here. To start with I would like to discuss difficult questions from October2012. The first question which I would like to discuss is

1. RCT conducted - improvement with cholinestrase drug 96/ 5050 and without cholinesterase 35/ 3035.

Calculate NNH:

The options were ( 136,140,146,150 the answers were in 100's) ( no one could do this as answer kept coming in fraction but not in 100's)

I would like to know who managed to solve this question, and discuss study design

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shall we start revising mcqs here?? I am starting with past paper questions. Does anyopne wants to join in so we can clarify our confusions.

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count me in.start posting questions DKK

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Yes it is a great idea, I think we should start critical appraisal study group here. To start with I would like to discuss difficult questions from October2012. The first question which I would like to discuss is

1. RCT conducted - improvement with cholinestrase drug 96/ 5050 and without cholinesterase 35/ 3035.

Calculate NNH:

The options were ( 136,140,146,150 the answers were in 100's) ( no one could do this as answer kept coming in fraction but not in 100's)

I would like to know who managed to solve this question, and discuss study design

If we calculate it answer is 133.3 or answer should be 136 if we use this as an example

The following is an example of calculating number needed to harm.

In a cohort study, individuals with exposure to a risk factor (Exposure +) are followed for a certain number of years to see if they develop a certain disease or outcome (Disease +). A control group of individuals who are not exposed to the risk factor (Exposure −) are also followed . "Follow up time" is the number of individuals in each group multiplied by the number of years that each individual is followed: Disease + Total subjects followed Years followed^ Follow-up time Incidence Exposure + 6054 86318 13.56^ 1,170,074 0.0703 Exposure − 32 516 21.84^ 11,270 0.0620

^ "Years followed" is a weighted average of the length of time the patients were followed.

The incidence with exposure is: 9afd407f4f3fb2b49f3874013791952a.png

The incidence without exposure: db459ff0ca6a604c612654c13ac1fa8a.png

To determine the relative risk, divide the incidence with exposure by the incidence without exposure: e4529140a090c1e296f329104ec42566.pngrelative risk

To determine attributable risk subtract incidence without exposure from incidence with exposure: 0.0703 − 0.0620 = 0.0083 = 0.83% = attributable risk

The number needed to harm is the inverse of the attributable risk, or: 4486b1711410a316064fc8e040436165.png = Number needed to harm

This means that if 120 individuals are exposed to the risk factor, 1 will develop the disease that would not have otherwise.

Note that these calculations can be affected enormously by roundoff error. (If no roundoff is used in the intermediate calculations above, the final figure for the NNH is 123.)

[edit] Number of exposures needed to harm

In case there can be more than one exposure in the specific period, the number (of patients) needed to harm is numerically equal to number of exposures needed to harm for one person if the risk per exposure isn't significantly altered throughout the specific period or by previous exposure, e.g. when the risk per exposure is very small or the "harm" is a very brief disease that doesn't confer immunity.

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Yes it is a great idea, I think we should start critical appraisal study group here. To start with I would like to discuss difficult questions from October2012. The first question which I would like to discuss is

1. RCT conducted - improvement with cholinestrase drug 96/ 5050 and without cholinesterase 35/ 3035.

Calculate NNH:

The options were ( 136,140,146,150 the answers were in 100's) ( no one could do this as answer kept coming in fraction but not in 100's)

I would like to know who managed to solve this question, and discuss study design

If we calculate it answer is 133.3 or answer should be 136 if we use this as an example

The following is an example of calculating number needed to harm.

In a cohort study, individuals with exposure to a risk factor (Exposure +) are followed for a certain number of years to see if they develop a certain disease or outcome (Disease +). A control group of individuals who are not exposed to the risk factor (Exposure −) are also followed . "Follow up time" is the number of individuals in each group multiplied by the number of years that each individual is followed: Disease + Total subjects followed Years followed^ Follow-up time Incidence Exposure + 6054 86318 13.56^ 1,170,074 0.0703 Exposure − 32 516 21.84^ 11,270 0.0620

^ "Years followed" is a weighted average of the length of time the patients were followed.

The incidence with exposure is: 9afd407f4f3fb2b49f3874013791952a.png

The incidence without exposure: db459ff0ca6a604c612654c13ac1fa8a.png

To determine the relative risk, divide the incidence with exposure by the incidence without exposure: e4529140a090c1e296f329104ec42566.pngrelative risk

To determine attributable risk subtract incidence without exposure from incidence with exposure: 0.0703 − 0.0620 = 0.0083 = 0.83% = attributable risk

The number needed to harm is the inverse of the attributable risk, or: 4486b1711410a316064fc8e040436165.png = Number needed to harm

This means that if 120 individuals are exposed to the risk factor, 1 will develop the disease that would not have otherwise.

Note that these calculations can be affected enormously by roundoff error. (If no roundoff is used in the intermediate calculations above, the final figure for the NNH is 123.)

[edit] Number of exposures needed to harm

In case there can be more than one exposure in the specific period, the number (of patients) needed to harm is numerically equal to number of exposures needed to harm for one person if the risk per exposure isn't significantly altered throughout the specific period or by previous exposure, e.g. when the risk per exposure is very small or the "harm" is a very brief disease that doesn't confer immunity.

Thanks Sajida, But the ans. I am getting is 125.

can you tell me how it is 133.3?

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Yes it is a great idea, I think we should start critical appraisal study group here. To start with I would like to discuss difficult questions from October2012. The first question which I would like to discuss is

1. RCT conducted - improvement with cholinestrase drug 96/ 5050 and without cholinesterase 35/ 3035.

Calculate NNH:

The options were ( 136,140,146,150 the answers were in 100's) ( no one could do this as answer kept coming in fraction but not in 100's)

I would like to know who managed to solve this question, and discuss study design

If we calculate it answer is 133.3 or answer should be 136 if we use this as an example

The following is an example of calculating number needed to harm.

In a cohort study, individuals with exposure to a risk factor (Exposure +) are followed for a certain number of years to see if they develop a certain disease or outcome (Disease +). A control group of individuals who are not exposed to the risk factor (Exposure −) are also followed . "Follow up time" is the number of individuals in each group multiplied by the number of years that each individual is followed: Disease + Total subjects followed Years followed^ Follow-up time Incidence Exposure + 6054 86318 13.56^ 1,170,074 0.0703 Exposure − 32 516 21.84^ 11,270 0.0620

^ "Years followed" is a weighted average of the length of time the patients were followed.

The incidence with exposure is: 9afd407f4f3fb2b49f3874013791952a.png

The incidence without exposure: db459ff0ca6a604c612654c13ac1fa8a.png

To determine the relative risk, divide the incidence with exposure by the incidence without exposure: e4529140a090c1e296f329104ec42566.pngrelative risk

To determine attributable risk subtract incidence without exposure from incidence with exposure: 0.0703 − 0.0620 = 0.0083 = 0.83% = attributable risk

The number needed to harm is the inverse of the attributable risk, or: 4486b1711410a316064fc8e040436165.png = Number needed to harm

This means that if 120 individuals are exposed to the risk factor, 1 will develop the disease that would not have otherwise.

Note that these calculations can be affected enormously by roundoff error. (If no roundoff is used in the intermediate calculations above, the final figure for the NNH is 123.)

[edit] Number of exposures needed to harm

In case there can be more than one exposure in the specific period, the number (of patients) needed to harm is numerically equal to number of exposures needed to harm for one person if the risk per exposure isn't significantly altered throughout the specific period or by previous exposure, e.g. when the risk per exposure is very small or the "harm" is a very brief disease that doesn't confer immunity.

Sorry the calculations are as follows

96/ 5050 =0.0190

35/ 3035=0.0115

0.0190-0.0115-=0.0074

1/0.0074 =135.1. for NNH figure should be rounded to lower number but that is not in option,I presume 136 should be the answer

please correct me if I am wrong

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Yes it is a great idea, I think we should start critical appraisal study group here. To start with I would like to discuss difficult questions from October2012. The first question which I would like to discuss is

1. RCT conducted - improvement with cholinestrase drug 96/ 5050 and without cholinesterase 35/ 3035.

Calculate NNH:

The options were ( 136,140,146,150 the answers were in 100's) ( no one could do this as answer kept coming in fraction but not in 100's)

I would like to know who managed to solve this question, and discuss study design

If we calculate it answer is 133.3 or answer should be 136 if we use this as an example

The following is an example of calculating number needed to harm.

In a cohort study, individuals with exposure to a risk factor (Exposure +) are followed for a certain number of years to see if they develop a certain disease or outcome (Disease +). A control group of individuals who are not exposed to the risk factor (Exposure −) are also followed . "Follow up time" is the number of individuals in each group multiplied by the number of years that each individual is followed: Disease + Total subjects followed Years followed^ Follow-up time Incidence Exposure + 6054 86318 13.56^ 1,170,074 0.0703 Exposure − 32 516 21.84^ 11,270 0.0620

^ "Years followed" is a weighted average of the length of time the patients were followed.

The incidence with exposure is: 9afd407f4f3fb2b49f3874013791952a.png

The incidence without exposure: db459ff0ca6a604c612654c13ac1fa8a.png

To determine the relative risk, divide the incidence with exposure by the incidence without exposure: e4529140a090c1e296f329104ec42566.pngrelative risk

To determine attributable risk subtract incidence without exposure from incidence with exposure: 0.0703 − 0.0620 = 0.0083 = 0.83% = attributable risk

The number needed to harm is the inverse of the attributable risk, or: 4486b1711410a316064fc8e040436165.png = Number needed to harm

This means that if 120 individuals are exposed to the risk factor, 1 will develop the disease that would not have otherwise.

Note that these calculations can be affected enormously by roundoff error. (If no roundoff is used in the intermediate calculations above, the final figure for the NNH is 123.)

[edit] Number of exposures needed to harm

In case there can be more than one exposure in the specific period, the number (of patients) needed to harm is numerically equal to number of exposures needed to harm for one person if the risk per exposure isn't significantly altered throughout the specific period or by previous exposure, e.g. when the risk per exposure is very small or the "harm" is a very brief disease that doesn't confer immunity.

Sorry the calculations are as follows

96/ 5050 =0.0190

35/ 3035=0.0115

0.0190-0.0115-=0.0074

1/0.0074 =135.1. for NNH figure should be rounded to lower number but that is not in option,I presume 136 should be the answer

please correct me if I am wrong

You are correct. As i was considering only 3 no.s after the decimal. If you take 4 no.s after decimal then ur ans is correct. My method of calculation in the exam is correct but it costed me exam.

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if only one can form a physical group.............................66days and counting.........

anyone wanna meet up please?

I'm between east and south east london and happy to travel some

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