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# Find the z-score that has 2.5% of the distributions area to

### Customer Question

Find the z-score that has 2.5% of the distribution’s area to its left.
The z-score is _ (round 2 decimal)
Submitted: 7 years ago.
Category: Math Homework
Expert:  muvee replied 7 years ago.
Customer: replied 7 years ago.

Part of the answer on the last one was cut off.. Here is the rest..Thank you

The table below shows the results of a survey in which 143 men and 145 women workers ages 25-64 were asked if the have at least one months income set aside for emergencies.

Men Women Total

Less than 1 come 66 84 150

One month's income or more 77 61 138

Total 143 145 288

Find the probability that a randomly selected worker has one mnt income or more set aside emergencies ( the probability is )_____ (round to the nearest thousandth)

Given that a randomly selected worker is a male, find the probaloity that the worker has less than one mnts income( the probability is )______ ( round to the nearest thousandth)

Given that a randomly selected worker has one mnts income or more, find the probability that the worker is a female(the probability is ) _____ ( round to the nearest thousandth)

Are the events" having less than one months's income saved" and being male? Independent or dependant

A researcher wishes to estimate with 99% confidence, the proportion of adults who have high speed internet access. Her estimate must be accurate within 3% of the proportion.

What is the minimum sample size needed using a prior study that found that 54% of the responde4nts said they have high-speed internet access?

N_ ( round up to the nearest whole number )

What is the minimum sample size needed assuming that no preliminary estimate is available ?

N_ ( round up to the nearest whole number )

Decide if the situation involves permutations, combinations or neither. Explain your reasoning.

The number of ways 17 ppl can line up in a row for concert tickets.

Choose the correct ans.

1. Permutations. The older of the 17 people in line matters

2. Neither. A line of peole is neither an ordered arrangement of objects, nor a selection of objects from a group of objects

3. Combinations. The order of the 17 ppl in line does not matter.

The responses of a sample of 1010 ppl who were asked if the air quality in their community is better or worse than it was 10 yrs ago are shown below. Find the mean, median, and mode

Better 350 Worse 420 Same 240

The mean ___

The median____

The correct mode: Better, worse or same

Researchers conducted experiments with trees. Listed below are weights of trees given no fertilizer and trees treated with fertilizer and irrigation.

Find the range, variance and std bdev for each two samples, them compare the two sets.

Does there appear to be a difference between the two styd dev?

No treatment 0.08 0.27 0.09 0.17 0.27

Fertilizer and irrigation 0.23 2.29 1.95 2.17 1.59

Range were give4n treatment = ____ kg

Range treated with fertilizer and irragtion ___ kg

Find the variance and std dev for the trees that were given no treatment____

Sample variance___ kg2 ( rnd to two decimal places)

Sample std dev ____ kg

Now find the variance and the std dev for the trees treated with fertilizer and irrigation.

Sample variance ___ kg2 ( rnd to three decimals)

Sample std dev ___ kg

Expert:  muvee replied 7 years ago.

I think you post same question on another thread. But I put solution again, just in case.

Customer: replied 7 years ago.

Thnx Muvee,

Can you finish number 8.. ?

The responses of a sample of 1010 ppl who were asked if the air quality in their community is better or worse than it was 10 yrs ago are shown below. Find the mean, median, and mode

Better 350 Worse 420 Same 240

The mean ___

The median____

The correct mode: Better, worse or same

Expert:  muvee replied 7 years ago.

Correction for #5

P(one month income or more)=138/288=0.79

P(less than 1 month income|male)=P(male and less than one month income)/P(male)=66/150=0.44

P(female| 1 month income or more)=P(female and one month income or more)/P(1 month income or more)=61/138=0.442
events" having less than one months's income saved" and being male are dependant

#8. median is same

mean is same

Customer: replied 7 years ago.
Are you sure beacuse the answer should be rounded to the thousandth
Expert:  muvee replied 7 years ago.

a typo:

the first result should be 0.479, not 0.79. Others are correct. I am sure.

Customer: replied 7 years ago.

Ok, Thank you for your help!

Expert:  muvee replied 7 years ago.
My pleasure.
Customer: replied 7 years ago.

Hi Muvee,

I have to redo these questions, they seem to be the same except the numbers are a bit different.. can you help me?

Expert:  muvee replied 7 years ago.
Sure, tell me when is due.
Customer: replied 7 years ago.
It's due now, am retyping them right I will send it over in just a sec... Thank you
Expert:  muvee replied 7 years ago.
ok.
Customer: replied 7 years ago.

Ok here it is..it may be a bit tricky, but the numbers have been changed ... I will add funds also for your help..ok

2. The responses of a sample of 1050 ppl who were asked if the air quality in their community is better or worse than it was 10 yrs ago are shown below. Find the mean, median, and mode

Better 347 Worse 460 Same 243

The mean ___

The median____

The correct mode: Better, worse or same

27. Find the z-score that has 30.5% of the distribution's area to its left.
The z-score is ___ (round 2 decimal)

9. In a recent year, scores on a standardized test for high school students with 3.50 to 4.00 grade point avg were normally distributed, with a mean of 37.4 and a std dev of 1.9. A student with 3.50 to 400 grae pt avg who took the standardized test is randomly selected.
Find the probability that the student's test score is less than 33?
Find the probability of a student scoring between 34.1 and 40.7 ?
Find the probability that the student's test score is more than 39.1 ?

21. You are given the sample mean and the sample dev. Use this information construct the 90% and 95% confidence intervals for the population mean. Which interval is what? If convenient, use technology to construct the confidence intervals.

A random sample of 44 gas grills has a mean price of 644.80 and std dev of 58.10

The 90% confidence interval is ____
The 95% confidence interval is ____
Which interval is wider? The 95% confidence interval or the 90% interval

24. People were polled on how many books they read the previous year. How many subjects are needed to estimate the number of books read the previous year within one book with 95% confidence? Initial survey results indicate that o= 18.3 books

A 95% confidence level requires ____ subjects (round up to a whole number)

18. The table below shows the results of a survey in which 142 men and 144 women workers ages 25-64 were asked if the have at least one months income set aside for emergencies.

Men Women Total

Less than 1 come 65 83 148

One month's income or more 77 61 138

Total 142 144 286

Find the probability that a randomly selected worker has one mnt income or more set aside emergencies ( the probability is )_____ (round to the nearest thousandth)

Given that a randomly selected worker is a male, find the probaloity that the worker has less than one mnts income( the probability is )______ ( round to the nearest thousandth)

Given that a randomly selected worker has one mnts income or more, find the probability that the worker is a female(the probability is ) _____ ( round to the nearest thousandth)

Are the events" having less than one months's income saved" and being male? Independent or dependant

23. A researcher wishes to estimate with 99% confidence, the proportion of adults who have high speed internet access. Her estimate must be accurate within 5% of the proportion.

What is the minimum sample size needed using a prior study that found that 34% of the respondents said they have high-speed internet access? N_ __( round up to the nearest whole number )

What is the minimum sample size needed assuming that no preliminary estimate is available ? N___ ( round up to the nearest whole number )

11. Researchers conducted experiments with trees. Listed below are weights of trees given no fertilizer and trees treated with fertilizer and irrigation.

Find the range, variance and std dev for each two samples, them compare the two sets.

Does there appear to be a difference between the two styd dev?

No treatment 0.07 0.13 0.35 0.08 0.03

Fertilizer and irrigation 0.31 1.22 0.28 0.29 2.42

Find the range for the tress that were given no treatment = ____ kg

Find the range for the trees treated with fertilizer and irrigation ___ kg

Find the variance and std dev for the trees that were given no treatment____

Sample variance___ kg2 ( rnd to two decimal places)

Sample std dev ____ kg

Now find the variance and the std dev for the trees treated with fertilizer and irrigation.

Sample variance ___ kg2 ( rnd to three decimals)

Sample std dev ___ kg

16. Calculate the correlation coefficient r, letting row 1 represent the x-values and Row 2 the y-values. Then calculate it again, letting Row 2 represent the x-value and Row 1 the y-values. What effect does switching the variables have on r? (changes sign, decreases, remains unchanged, increases )

Row1: 14 29 35 40 54 60 76
Row2: 206 118 197 173 153 119 139

Calculate the correlation coefficient r, letting row 1 represent the x-values and row 2 the y-values. R = ____ ( round to 3 decimal places as needed)

Calculate the correlation coefficient r, letting row 2 represent the x-values and row 1 the y-values. R= ____ (round to 3 decimal place as needed)

What effect does switching the variables have on the correlation coefficient?

The correlation coefficient(increases, decreases, changes signs, remains unchanged) when the x-values and y-values are switched.

15. The population mean and std dev are given below. Find the required probability and determine whether the given sample mean would be considered unusual.

For a sample of n= 65, find the probability of a sample mean greater than 215 if u=214 and o= 3.6 is ? ( round to two decimal places)

Would the sample mean be considered unusual?

The sample mean(would, would not) be considered unusual because it (lies, does not lie) within (1 std dv, 2 std dv, 3 std d) of the mean of the sample means.

19. Identify the class width, class midpoints, and class boundaries for the given frequency distribution.
40-42 1
43-45 3
46-48 5
49-51 11
52-54 7
55-57 7
58-60 1

What is the class width ?

What are the class midpoints?

What are the class boundaries?

29. The state test scores for 12 randomly selected hs seniors are shown on the right.
1423 1226 989
691 730 839
726 750 540
630 1442 941

Find the sample
Find the standard deviation
A 90% confidence interval for the population mean u is _ (round to 1 decimal place)

6. The weights(in pounds) of 6 vehicles and the variability of their braking distances(in feet) when stopping on dry surface are shown in the table. Can you conclude that there is a significant linear correlation between vehicle weight and variability in braking distance on dry surface? Use a=0.01

Weight x 5950 5380 6500 5100 5880 4800

Braking distance y 1.73 1.97 1.94 1.57 1.63 1.50

Can you conclude that there is a significant linear correlation?

No,there Is not enough evidence at the 1% level to conclude that there is a significant linear correlation

Yes, there is enough evidence at the 1% level to conclude that there is a significant linear correlation

No, there is not enough evidence at the 1% level conclude there is no significant linear correlation

Yes, there is enough evidence at the 1% level to conclude that there is no significant linear correlation.

Thanks

Customer: replied 7 years ago.
How's it going?
Expert:  muvee replied 7 years ago.

Solution

Customer: replied 7 years ago.
Omgsh, allot of these were incorrect... thanks for help anyways
Expert:  muvee replied 7 years ago.
I think many of them are rounding problems. So when you compare it with software answer, it cannot 100% match.
Customer: replied 7 years ago.
Yea, i think so.
Expert:  muvee replied 7 years ago.
I typed so much in order to make oyu understand the steps to solve the questions, so final result is not as important as process.
Customer: replied 7 years ago.
I see, ok..makes sense.. thanks again.. Princess A
Expert:  muvee replied 7 years ago.
Are you working on the online statistical questions, not homework by hand?
Customer: replied 7 years ago.

Yes, I am working these statistical problems online!

Expert:  muvee replied 7 years ago.
ok, that why even a samll rounding error will cause the entire answer be wrong.
Customer: replied 7 years ago.
Yep! the professor confirmed that the online problems are like that!!
Expert:  muvee replied 7 years ago.
Let me if you have any other questions.