Data Sufficiency

Please, check this out:
Thanks
Silvia

given 90 % attended first day

statement 1)1000 people registered for seminar
so 900 came for first day but we dont have any information about seconday day

statement 2)
let poulation be X
so second day attendance 0.8x i.e 80% of X
we know that first day attendance for seminar ewas 0.90 x i.e 90 % of x
so as the answer wanted is in % we can solve this
as 0.10 X didint came first day and 0.2 didnt came secon day
so only statement 2 is sufficient

amising6 wrote:given 90 % attended first day

statement 1)1000 people registered for seminar
so 900 came for first day but we dont have any information about seconday day

statement 2)
let poulation be X
so second day attendance 0.8x i.e 80% of X
we know that first day attendance for seminar ewas 0.90 x i.e 90 % of x
so as the answer wanted is in % we can solve this
as 0.10 X didint came first day and 0.2 didnt came secon day
so only statement 2 is sufficient

Amising,
In stm 1, we have 1,000 people registered for both days, so, stm2 tells us that 800 came on the second day, can't we calculate the percentage with 900 and 800?
Thnx
Silvia

Hey Silvia,

(1) tells us the total # of people registered, but doesn't tell us anything about the second day, so we can't determine what percentage of people didn't attend on either day. INSUFFICIENT

(2) tells us that 80% of those registered attended on the second day, but doesn't tell us anything about how many people attended on both days.

Remember, there could be an overlap between the two groups. In fact, there has to be an overlap in this case. The giveaway is that 90% attended on the first day, 80% on the second day. If the groups were totally separate, that would make for a total of 170%, which makes no sense. So there has to be some overlap.

You could represent this with a Venn Diagram that includes overlapping circles for "first day" and "second day". But the overlap could be many things, and thus the percentage of people who didn't go either day (i.e. the "neither" group of the Venn Diagram) could be many things. INSUFFICIENT

(1) and (2) together still don't tell us about the overlap. INSUFFICIENT

Make sense?

raz1024 wrote:Hey Silvia,

(1) tells us the total # of people registered, but doesn't tell us anything about the second day, so we can't determine what percentage of people didn't attend on either day. INSUFFICIENT

(2) tells us that 80% of those registered attended on the second day, but doesn't tell us anything about how many people attended on both days.

Remember, there could be an overlap between the two groups. In fact, there has to be an overlap in this case. The giveaway is that 90% attended on the first day, 80% on the second day. If the groups were totally separate, that would make for a total of 170%, which makes no sense. So there has to be some overlap.

You could represent this with a Venn Diagram that includes overlapping circles for "first day" and "second day". But the overlap could be many things, and thus the percentage of people who didn't go either day (i.e. the "neither" group of the Venn Diagram) could be many things. INSUFFICIENT

(1) and (2) together still don't tell us about the overlap. INSUFFICIENT

Make sense?

Makes complete sense Raz_1k, and by the way, that was the OA
Thanks for your time to you both guys ...
Silvia.