#### HLHLO

##### New Member
I am taking an online college course for Statistics and I am struggling..
I find it really hard to teach yourself statistics without a teacher's involvement, but online is my only option with working. This is my last semester, so I do not want to mess it up. If anyone can help explain how to solve these problems, I would greatly appreciate it.

20. Laura asks whether attending a private school versus a public school leads to higher or lower performance on a test of social skills. A sample of 100 students from a private school produces a mean of 71.30 on the test, and the mean for the population of students from a public school is 75.62(σX=28.0). (a) Should she use a one-tailed test or a two-tailed test? Why? (b) Using symbols, what are Ho and Ha? (C) Compute Zobt. (d) With α=.0, what is Zcrit? (e) What should she conclude about this relationship?

12. A researcher predicts that smoking cigarettes decreases a person’s sense of smell. On a test of olfactory sensitivity, the µ for nonsmokers is 18.4. A sample of 12 people who smoke a pack a day produces x¯=16.25, s2x=4.75. (a) What are Ho and Ha for this study? (b) Compute tobt. (c) What is your tcrit? (d) What should the researcher conclude about this relationship? (e) Report your results using the correct format. (f) Compute the confidence interval for µ if appropriate?

Thank you in advance. My assignment is not due until Sunday so I will try my best to figure this out.

#### StilloftheNight

##### New Member
Does question 20 give the standard deviation for the private school students? I only see the mean given. In order to find the test statistic "Zobt" you usually need the mean and standard deviation of both of the populations, that being from private school and public school. The questions looks as though it is trying to compare social skill performance amongst TWO POPULATIONS. Also, you mentioned alpha is equal to .0 what? .05 .025 etc.?

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#### statsforpsychyinstructor

##### New Member
I am taking an online college course for Statistics and I am struggling..
I find it really hard to teach yourself statistics without a teacher's involvement, but online is my only option with working. This is my last semester, so I do not want to mess it up. If anyone can help explain how to solve these problems, I would greatly appreciate it.

20. Laura asks whether attending a private school versus a public school leads to higher or lower performance on a test of social skills. A sample of 100 students from a private school produces a mean of 71.30 on the test, and the mean for the population of students from a public school is 75.62(σX=28.0). (a) Should she use a one-tailed test or a two-tailed test? Why? (b) Using symbols, what are Ho and Ha? (C) Compute Zobt. (d) With α=.0, what is Zcrit? (e) What should she conclude about this relationship?

12. A researcher predicts that smoking cigarettes decreases a person’s sense of smell. On a test of olfactory sensitivity, the µ for nonsmokers is 18.4. A sample of 12 people who smoke a pack a day produces x¯=16.25, s2x=4.75. (a) What are Ho and Ha for this study? (b) Compute tobt. (c) What is your tcrit? (d) What should the researcher conclude about this relationship? (e) Report your results using the correct format. (f) Compute the confidence interval for µ if appropriate?

Thank you in advance. My assignment is not due until Sunday so I will try my best to figure this out.
There are weird symbols in question 1 so I don't know what the information given is..but question 2...

t= M-µ
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s/square root of n

you have variance, s2..so you take the square root to get sample s.d ..you get 2.18

so t= 16.25 - 18.4
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0.63