Saturday, July 4, 2009

Practice problems for homework due 7/6

Take the information of this incomplete contingency table with categories left and right in the columns and yes and no in the rows and fill in the rest of the table using the degrees of freedom.


____________left____right_____row totals
Yes___________25________________75
No____________________50_______
col. totals___90_____________________grand total

Use the information from the completed table to find the following probabilities, both as fractions and as percents rounded to the nearest tenth of a percent.

p-hat(Yes) =

p-hat(Left) =
p-hat(Left and Yes) =

p-hat(Left or Yes) =

p-hat(Left, given Yes) =

p-hat(Yes, given Left) =

State the following complementary sets without using the word NOT, using the categories from above.

NOT (Left) =

NOT (Left or Yes) =

NOT(Right and Yes) =

Answers in the comments.

4 comments:

Prof. Hubbard said...

____________left____right_____row totals
Yes___________25______50________75
No____________65______50________115
col. totals_____90_____100________190 grand total

Use the information from the completed table to find the following probabilities, both as fractions and as percents rounded to the nearest tenth of a percent.

p-hat(Yes) = 75/190 = 29.5%

p-hat(Left) = 90/190 = 47.4%

p-hat(Left and Yes) = 25/190 = 13.2%

p-hat(Left or Yes) = 75/190 + 90/190 - 25/190 = 140/190 = 73.7%

p-hat(Left, given Yes) = 25/75 = 33.3%

p-hat(Yes, given Left) = 25/90 = 27.8%

State the following complementary sets without using the word NOT, using the categories from above.

NOT (Left) = Right

NOT (Left or Yes) = Right and No

NOT(Right and Yes) = Left or No

Moira said...

will you be going over this in class again (and, or, given) & complements?

re: practice homework & complementary sets

NOT(left or yes)...i intuited
(right or No)...after checking comments, I see I was wrong...then checked the reasoning by eliminating values that would not fit the set: NOT(left or Yes)....-->(RT and No)=rt-no=50...

for NOT(Rt and Yes)--->i thought it was (Left and No)=65...if (Left or No) and I use p(Lt or No) formula to ck answer, I come up w/ 65.8% (BOX w/left-no value=65)

how best to ck answers? process of elimination? i'm thinking we don't use the [and, or, given] frequency formulas to find/verify complementary sets?

Moira said...

sorry, i'm a bit confused by complimentary sets. will review my notes again, and check last years lecture notes as well. thank you!

Dr. Jep said...

I thought I was okay until I read these comments, now I am some-what confused also. I hope you will go over this in class, please.