Question

For the following question(s): Professor Juarez thinks the students in her statistics class this term are more creative than most students at this university. A previous study found that students at this university had a mean score of 35 on a standard creativity test. Professor Juarez finds that her class scores an average of 40 on this scale, with an estimated population standard deviation of 7. The standard deviation of the distribution of means comes out to 1.63.

4. What is the t score?
A) (40  35)/7 = .71
B) (40  35)/1.63 = 3.07
C) (40  35)/72 = 5/49 = .10
D) (40  35)/1.63

Answer 1

5. What effect size did Professor Juarez find?
A) (40  35)/7 = .71
B) (40  35)/1.63 = 3.07
C) (40  35)/72 = 5/49 = .10
D) (40  35)/1.632 = 5/2.66 = 1.88

Answer 2

@jim_thompson5910 Can you double check these? I got 4. B and 5. A

Answer 3

What's with the squiggle mark over the 40?

Answer 4

I don't know it's supposed to be a -

Answer 5

so like a bar over 40?

Answer 6

it's supposed to be (40-35)/7 and so forth

Answer 7

oh i see

Answer 8

4 B looks good, but again, I have no idea about the effect size...so idk what to do with 5

Answer 9

Ok.. can I show you a few more that I am unsure about?

Answer 10

go ahead

Answer 11

For the following question(s): A school counselor claims that he has developed a technique to reduce prestudying procrastination in students. He has students time their procrastination for a week and uses this as a pretest (before) indicator of procrastination. Students then attend a workshop in which they are instructed to do a specific warming-up exercise for studying by focusing on a pleasant activity. For the next week, students again time their procrastination. The counselor then uses the time from this week as the posttest (after) measure.

7. Suppose the counselor wants to examine whether there is a change of any kind (either an increase or decrease) in procrastination after attending his workshop. What would be the appropriate description of “Population 2” (the population to which the population his sample represents is being compared)?
A) People whose posttest scores will be lower than their pretest scores
B) People whose change scores will be greater than 0
C) People whose change scores will be 0
D) People whose change scores will be less than their pretest scores






8. Presume the counselor wants to examine whether there is a change (either an increase or decrease) in procrastination after attending his workshop. If the counselor tests 10 students using the .05 level of significance, what cutoff t score(s) will he use? (You should be able to figure this out without a table.)
A) 2.62, 0, +2.62
B) +2.262
C) 2.262, 0
D) 2.262, +2.262



9. Suppose the counselor found the sum of squared deviations from the mean of the sample to be 135. Given that he tested 10 people, what would be the estimated population variance?
A) 135/10 = 13.5
B) 135/9 = 15.0
C) 10/135 = .074
D) 9/135 = .067




10. A researcher conducts a study of perceptual illusions under two different lighting conditions. Twenty participants were each tested under both of the two different conditions. The experimenter reported: “The mean number of effective illusions was 6.72 under the bright conditions and 6.85 under the dimly lit conditions, a difference that was not significant, t(19) = 1.62.”

Explain this result to a person who has never had a course in statistics. Be sure to use sketches of the distributions in your answer.

Answer 12

The only one I think I know is 9) b

Answer 13

population variance = (sum of squared deviations)/N

where N is the population size

Answer 14

which one are you talking about?

Answer 15

For #9

Answer 16

so it's over 10? for some reason I thought it was N-1

Answer 17

you're thinking of the sample variance

Answer 18

or sample standard deviation

Answer 19

OO.. so my answer would be A then

Answer 20

yes

Answer 21

Gotcha.. how do I figure out the others?

Answer 22

I'm not sure about 7. I'll have to come back to that.

Answer 23

For #8, I think you have to find the value k that satisfies this equation

P(T < k) = 0.025

with 10-1 = 9 degrees of freedom

Answer 24

What do the letters stand for?

Answer 25

T is a random variable from the T distribution

Answer 26

do you have a T distribution table?

Answer 27

No.. it says I should be able to figure it out without a table

Answer 28

you either need a table or calculator

Answer 29

there's no way to do it by hand (at least in a reasonable amount of time)

Answer 30

Think I can google a test?

Answer 31

here's one good calculator you can use

http://www.usablestats.com/calcs/tinv

Answer 32

What number do I enter for proportion? and this is 2 tailed right because they are asking for 2 numbers?

Answer 33

you can enter 0.05 and make it 2 sided

if it were one sided, then you'd enter 0.025 (since 0.05/2 = 0.025)

Answer 34

so my answer would be B

Answer 35

keep in mind this is a two tailed test

Answer 36

Ok.. so d?

Answer 37

good

Answer 38

Are you able to help with 7 and 10?

Answer 39

I'm not sure about 7 still. I think the claim that the scores would be lower would indicate he wants population 2 to have lower scores, but I don't think that's how you'd define population 2

Answer 40

I might be missing something about it

Answer 41

Alright... thank you for all your help

Answer 42

you're welcome