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Re: In 1987 sinusitis was the most common chronic medical condition in the [#permalink]
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krndatta wrote:
KarishmaB Ma'am,

Please help me understand some basics in this question.

The incidence rate of S is same for all age groups. This means that S can occur to any person from ages 5 to 55.
The incidence rate of A and BP increases with age. This means that as the person's age increases then the incidence of A and BP increases. In other words, a person aged 5 to 20 might not develop A and Bp, but a person aged 55 will definitely do.


It is about probabilities. A person aged 5 to 20 will have a low probability of developing A or Bp but aged 55 will have a higher probability of developing them.

If incidence of S is the same for all age groups, it means in the set of people who have S, there will be people of all age groups. For every age, the probability is the same.

So the set of people who have S will be a sample of the population without any age bias. If there is a 20% incidence rate of S (same for all age groups) and there is a population of 100 people (20 children, 30 youth, 30 adults, 20 old), the set of people with S will likely be 20 people (4 children, 6 youth, 6 adults, 4 old). So the average age of this set of people will be similar to the average age of the population.

In contrast, note that average age of set of people having A or Bp will be higher since incidence of these diseases is higher among the older people.
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In 1987 sinusitis was the most common chronic medical condition in the [#permalink]
KarishmaB Ma'am,

Quote:
So the set of people who have S will be a sample of the population without any age bias. If there is a 20% incidence rate of S (same for all age groups) and there is a population of 100 people (20 children, 30 youth, 30 adults, 20 old), the set of people with S will likely be 20 people (4 children, 6 youth, 6 adults, 4 old). So the average age of this set of people will be similar to the average age of the population.


In this we are assuming that the age is same for all age groups. I mean the we are taking the age of children, youth, adults, and old to be the same.

Am I right?
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Re: In 1987 sinusitis was the most common chronic medical condition in the [#permalink]
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krndatta wrote:
KarishmaB Ma'am,

Quote:
So the set of people who have S will be a sample of the population without any age bias. If there is a 20% incidence rate of S (same for all age groups) and there is a population of 100 people (20 children, 30 youth, 30 adults, 20 old), the set of people with S will likely be 20 people (4 children, 6 youth, 6 adults, 4 old). So the average age of this set of people will be similar to the average age of the population.


In this we are assuming that the age is same for all age groups. I mean the we are taking the age of children, youth, adults, and old to be the same.

Am I right?


You can make the data as granular as you wish to. Only for ease have I divided them into 4 groups of children, youth, adult and old. I could divide them into 100 grps of 1 yr old, 2 yr old, 3 yr old etc and still the logic remains the same.
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Re: In 1987 sinusitis was the most common chronic medical condition in the [#permalink]
Is inference question and derive conclusion questions the same?

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Re: In 1987 sinusitis was the most common chronic medical condition in the [#permalink]
KarishmaB wrote:
ajit257 wrote:
In 1987 sinusitis was the most common chronic medical condition in the United States, followed by arthritis and high blood pressure, in that order.
The incidence rates for both arthritis and high blood pressure increase with age, but the incidence rate for sinusitis is the same for people of all ages.
The average age of the United States population will increase between 1987 and 2000.

Which of the following conclusions can be most properly drawn about chronic medical conditions in the United States from the information given above?
(A) Sinusitis will be more common than either arthritis or high blood pressure in 2000.
(B) Arthritis will be the most common chronic medical condition in 2000.
(C) The average age of people suffering from sinusitis will increase between 1987 and 2000.
(D) Fewer people will suffer from sinusitis in 2000 than suffered from it in 1987.
(E) A majority of the population will suffer from at least one of the medical conditions mentioned above by the year 2000.

I am having some difficulty in drawing conclusion questions. Please can some provide some helpful pointers to tackle such questions.. thanks.


One important point you need to understand to understand this question is the increase in average age of a population.
Lets say average age of US population is 40 yrs. (Add ages of all people and divide by the number of people). The average age need not increase with time (it can even reduce e.g. when life expectancy decreases; people live shorter lives; lots of new babies are born) If average age increases to 50 yrs, it means people are living longer lives or not many new babies are being born or both (a problem being faced by much of the developed world today)
So when we say average life increased, it is probably because there are more aged people.

Premises:
- In 1987 sinusitis most common chronic condition followed by arthritis and high blood pressure
- More arthritis and high blood pressure with age
- Incidence of sinusitis is the same for people of all ages
- Average age will increase between 1987 and 2000.

Let's refresh what we said about conclusion questions - should be implied from the argument and should give no new data.

(A) Sinusitis will be more common than either arthritis or high blood pressure in 2000.
With increase in average age, we cannot say this. It is possible that other two become more common.

(B) Arthritis will be the most common chronic medical condition in 2000.
Definitely no reason to pick Arthritis out of the two - BP and Arthritis so no need to even think about it.

(C) The average age of people suffering from sinusitis will increase between 1987 and 2000.
Since incidence of sinusitis is the same for all ages, we can conclude that the average age of a person suffering from Sinusitis is the same as the average age of the population. Since average age of population will increase, average age of people suffering from Sinusitis will also increase.

(D) Fewer people will suffer from sinusitis in 2000 than suffered from it in 1987.
Sinusitis does not depend on age so cannot be concluded.

(E) A majority of the population will suffer from at least one of the medical conditions mentioned above by the year 2000.
No reason to conclude this.




Here- what if the the incidence of sinusitis is more common amongst the younger cohort? Would even then an increase in the average age also increase the incidence of sinusitis ? I fail to understand why is E wrong.
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Re: In 1987 sinusitis was the most common chronic medical condition in the [#permalink]
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