SOCI 3311 Blog

Can someone please explain to me how to do this problem? I am having trouble determining how to do this.

I don't get Assignment 5
1.4
when did we ever talk about z score conversion?


also is this okay for number 5?
5.
H(0): The crime rate is independent of outdoor temperature.
H(1): The crime rate is dependent on the outdoor temperature.
X2 obtained = 29.26
alpha level =.05
Df = 4
X2 critical = 9.49
Decision: reject the null, the crime rate is dependent on the outdoor temperature.

it doesn't make sense that temperature can affect crime rate. I might be doing something wrong. Anyone?

I do not understand Degrees of Freedom. I have read unit 10 and still can not read the information to understand the following questions. Please help...
Answer 2:6 N-1, 2:7 Population ?

Is 2-7 the chi square test?

Can someone please help me with these? I'm having a little trouble with them is:
4-1. is it suppose to say positive correlation instead of high?
4-2. I'm not sure about this one at all?

Can someone tell me if I have these correct please?
1-3. False
1-5. True

How do we type in certain symbols such as the symbol for the estimate of the standard deviation of sample mean differences? I'm not sure how to put the subscript of "d" after the "s".
Thanks!

OK I KNOW IM FULL OF QUESTIONS TONIGHT BUT I CANT AFFORD TO LOSE ANY MORE POINTS..

FOR QUESTIONS 3, MY X VARIABLES WOULD BE THE POWERBOATS REGISTRATION, AND MY Y WOULD BE MANTEE KILLED CORRECT?
THESE ARE MY ANSWERS FOR SOME OF QUESTION 3 IS THIS RIGHT?
3.3) STRONG RELATIONSHIP
3.4) 605.424
3.5) 0.76%

ALSO, IS ANYONE ELSE HAVING PROBLEMS USING THE CORRELATION ANALYSIS CALCULATOR FOR SOME REASON AFTER I PLACE MY DATA IN AND HIT CALCULATE NOTHING HAPPENS! I MAY BE DOING SOMETHING WRONG MOST LIKELY.. THANKS!

I JUST WANT TO CHECK MY ANSWERS

1-1 I HAVE TRUE
1-6 I HAVE FALSE
2-10 I HAVE CONTINGENCY

2-9 IM A LITTLE CONFUSED IS IT 20? FOR SOME REASON I CANT SEEM TO GET THIS BUT ONCE SOMEONE ANSWERS IT IM SURE IT WILL BE CLEAR THEN LOL.. THANKS

Hey Dr. Guy, I wanted to check some of the answers I got on the homework assignment.

1.5 true
1.7 true
1.8 false
1.9 false
1.10 false

Also, for 3.5, do we list our answer as a percent (since it's a proportion) or leave it as the decimal we get by squaring r?

For 4.2, I saw in an earlier blog post the answer, but I don't understand why there is no label attached. The correlation is listed as r=.23 bushels? What am I missing?

Thanks so much!!

Could someone please tell me if the square root of the error variance is also called the standard erro of the estimate? Thanks.

1-2. True
1-8. True
1-9 True
2-8. Analysis of Variance?

I wasn't sure about 2-8.

Dr. Guy,
Where do we get our t-critical from? I have no idea where it is coming from except from the table I saw from in the unit....but the df only goes to 25 there. Thanks. :-)

Goodmorning Dr.Guy for question 2-2 would the answer be perfect relationship correlation.

OK IM SORRY IF THIS IS A DUMB QUESTION BUT CAN SOME ONE PLEASE TELL ME HOW TO PLACE THE SYMBOLS IN OUR JOURNALS? I HAVE BEEN WRITING THEM OUT THANKS

I was just wondering if these answers are correct:
1-6. False
1-10. True
2-2. samples
2-4. summed

For the table do we just but the df, sum of the square and mean of the square? Or do we have to go in more depth?

Hi Dr.Guy after i use the t test raw data calculator and got the calculations but what calculator do i use to get t obtain, this is were im stuck. thanks

Hi I can't figure these questions out. Can someone please explain them.

1. A random sample of 30 households was selected as part of a study on electricity usage and the number of kilowatt-hours (KWh) was recorded for each household in the sample for the March quarter of 2006. The average usage was found to be 375kWh (s=81 kWh). Assuming that usage is normally distributed, provide an expression for computing a 99% confidence interval for the mean usage in the March quarter of 2006. Correct answer: 375+- 40.73


2. To obtain an estimate of the proportion of ?full time? university students who have a part time job in excess of 20 hours per week, student union staff members decide to interview a random sample of full time students. They want the length of their 95% confidence interval to be no greater than 0.1. What size sample should be taken?

N ≅ 96
N ≅ 384
N ≅ 1000

3The recommended retail price of a brand of designer jeans is $150. The price of the jeans in a sample of 16 retailers is on average $141 with a sample standard deviation of 4. If this is a ?random? sample and the prices can be assumed to be normally distributed, construct a 95% confidence interval for the average sale price.

$141 ± $2.13
$141 ± $1.96
$141 ± $2.58
$141 ± $1.56

(I keep getting 141 +- 1.96 and the answer is 141+- 2.13, what am I doing wrong)

4.What is the smallest sample size required to provide a 95% confidence interval for a mean, if it is important that the interval be no longer than 1cm (i.e. margin of error = .5)? You may assume that the population is normal with a variance of 81cm.

N = 1245
N = 95
N = 34
N = 139

I plug everything into the formulas given in the unit and I am not coming up with any of these answers.

I just wanna make sure I got these answers right

3.H(0): μ(1) = μ(2)
H(1): μ(1) ≠ μ(2)
α = .05
t critical (df=10) =± 2.228
t obtained = .6632
Fail to reject H(0)

4.H(0): μ(1) = μ(2)
H(1): μ(1) ≠ μ(2)
α = .05
t critical (df=60)= ±2.00
t obtained= -2.45
Reject H(0)

H(0): μ(1) = μ(2)
H(1): μ(1) ≠ μ(2)
α = .05
t critical (df= 118) = ±1.98
t obtained = 4.44
Reject H(O)

5.

I'm not sure if I did this problem right

if there is two sets of data are you suppose to use the two-tail or one-tail t-test.

This is what I got for number 3

Level of significance =.05
t critical (df=10) =2.228-two tail test or one tail test 1.812)
t-obtained= .6632

is this anywhere close to the right answer?

Dr. Guy,
I am a little confused on #'s 3 and 4 from Assignment #4. I have searched on the blog, but am unable to find any help. Can you help me out or tell me where to look for this information? Thanks for your help.
Brandy Udashen

Hey Dr. Guy,

Are the answers for 1-1, 1-4, & 1-7 all FALSE?

One more question Dr. Guy, for question 1-3 it stated when the degrees of freedom are small, the distribution is somewhat flat and spread out. Now according to the text its stated that when the degree is equal to one that it will be more flat and spread out, not how small the number had to be, so would your statement be false.

I read the previous blog about this question because you have to convert the mean to inches. When I entered the information into the calculator

N= 26
Population Mean=5.833
Standard Deviation=5

I got the answer 5.83 plus or minus 2.15. Is that correct. I saw on the previous blog that the answer was 5.83 plus or minus 0.18.

If the 5.83 plus or minus .18 is the correct answer could you explain to me how.

Hi Dr. Guy, i wanted to know if i was on the right track with these questions.

1-8.false
1-9.true

2-5. i got 5, do we subtract 25-20 or 20-25 to get the degree of freedom
2-8. total variance estimate
2-9. between variance estimate
2-10.within variance estimate

Can anyone please explain how to solve this problem?
The probability is .3 that the mean of a sample of 36 terms from an infinite distribution (μ = 155 and σ = 40) will exceed what number?

The answer is 175.80

Could someone please explain to me how the z obtained value =3.33?

Is the z obtained value= 10.00? And if so, this would mean that the H(0) is rejected because it varies more than .01 of the z-critical right?

I want to make sure I have calucated the answers on number 9 correctly. (I'm not sure if I calcuated 9-2 and 9-3 correctly because I wasn't sure how to enter in the mean on both of these since they were in feet and inches, so I may have done them completely wrong??! If I did, could you please help me as to what I enter in the calculator as the mean?) Thank you!
9-2 5.83 ± 0.18
9-3 5.33 ± 2.58
9-4 14.00 ± 1.11
9-5 115.00 ± 5.16

Dr. Guy.
I just want to know before I take the quiz if these answers are correct. I want to make sure I do understand how to use the formula properly.

3.2 H(0)μ =42,500 AND H(1)= ≠ 42,500

4. H(0) μ =100
H(1) ≠ 100
α=0.1
z-critical = ± 2.58
z-obtained = 3.33
decision to reject H(0) and accept H(1)

5. H(0) μ = 21
H(1) = ≠ 21
α=0.5
z-critical = ± 1.96
z-obtained= -3.43
Decision to reject H(0) and accept H(1)


6 H(0)μ =13
H(1)= ≠ 13
α =0.05
z-critical = ± 1.96
z-obtained = 2.5
Decision to reject H(0) and accept H(1)

7 H(0) μ = 4
H(1) ≠ 4
α =0.01
z-critical = ± 2.58
z-obtained =1.304
Decision is do not reject H(0) and reject H(1)

How do you solve this? Do you need the number 36 or is it just to trick you?

unit 6.
2. The probability is .3 that the mean of a sample of 36 terms from an infinite distribution (μ = 155 and σ = 40) will exceed what number?

can anyone help this may sound stupid but i am having an issue. Are we suppose to logically guess or are we actually calculating something. Thanks

I don't seem to understand this question. Is it asking if the degrees of freedom is N-1. Or does it have something to do with the t value?

Dr. Guy,

I'm really not understanding how to do these problems. I've read the blogs and the section where it explains it in Unit 7. Can you break it down for me???

Thanks

hi Dr. Guy i was just wondering if i was putting these computations in the calculator right. im not sure if these are the right answers they look funny, not like in the chapter.

8-1. 110.00plus or minus 2.24
8-2. 77.00 plus or minus 3.59
8-3. 1.40 plus or minus 4.36
8-4. 72 plus or minus 3.53
8-5. 135.00 plus or minus 2.94

are these right.

On problem 9-2 & 9-3 how exactly to you compute the population mean???

On #10, where do i find the link to STATISTICAL TABLES to start working out this problem???

Dr. Guy,

I've read the other blogs on this question but I'm not understanding how you arrived at the answer or how you even began. I tried using the calc but I did'nt know what numbers go in the bottom two slots.

What is the difference between a test statistic and a critical statistic?

Hey Dr. Guy I was just wondering if I got the correct answers...
1-1 true
1-2 false
1-3 false
1-5 true
1-6 false
1-7 false

They were kind of worded tricky....

Thanks!!!

For 7-2, I used .3 as the z score and 0 as the other z score and came up with 11.791%. Is this correct? Also is 7-4 68% and 7-5 95%? I'm a little confused. Thank you!

Hey Dr. Guy I read previous blogs on how to work out questions 8 & 9, but my question is why or how do we get z = 1.96 for 8 and 2.58 for 9??? I'm getting different values for both. They are close the values in the blog, but for example #8 I get Z = 1.65
Another question I have is on #5 I am getting -3.43 for z-obtained and I don't know why. Please directed me in the right direction.

Hi just wanted to see if i had the right answers to these questions they were worded a little tricky from the way that they are in the book.
1-2 false ,because if the chances that u may pick up a queen would be 4/52 but once you simplify it u get 1/52. help
1-4 true
1-8 true
1-9 true
1-10 true

2-2. 1
2-5 test statistics

If you use the equation to turn the numbers into z scores and then find the area does the final answer equal 3.13%?

I know it's late but these are the only problems that I don't understand how to compute the answer.

Help please!

Could someone explain to me how to go about doing this question, i think i have an idea but i want to make sure im doing it right, kind of confused. Thanks

On the multiple choice practice quiz..
#5 How many terms are in an approximately normal distribution in which 150 terms have z scores above 1.35?
#7 Similar to above.
I dont understand how to solve these.

10-1. 65.542%
10-2. 5.48%
10-3. 126.75

Are these correct Dr. guy I used the formulas from the blog posted previously

I believe that 1-5 is true I just wanted to make sure that was correct. Also with 2-9 I got 22.73 or 15.8 is this correct?

I have yet to find the answer to this question, and I have read both chapters thoroughly. Am I looking past something? Help please!

How do you calculate the variance if there is no raw data ∑X2=150 and ∑X=25 for a population of 10 scores

can someone please explain to me how to get the variance?

Dr. Guy,
When I go to the standard normal curve calculator, I click on it, it opens, and I keep getting a white screen (blank), with a blank gray box on the screen. Can you help me out? I'm trying to complete #6 on Assignment 2. Thanks!
Brandy Udashen

Has anyone worked this problem from the practice quiz-What is the variance for the following frequency distribution (followed with a data set)?

It says the answer is 3.17. I keep getting 8.17. Help!!!

Hey Dr. Guy,

I was wondering if my explanation was good enough for this question. I answered:
"It cannot be negative because there is no upper limit therefore it cannot go below zero in value."

I was just wondering if the correct answers are [2-1] squared and [2-4] variance. Seems like the same definition is listed twice.