statistics test #2 revised

Pataasin ang iyong marka sa homework at exams ngayon gamit ang Quizwiz!

when finding the confidence interval and it is a proportion (z-test) what number do we use to determine the number of success and failures?

10

Suppose a simple random sample of 150 students is drawn from a population of 3000 college students. Among sampled students, the average IQ score is 115 with a standard deviation of 10. What is the point estimate?

115

The width of a confidence interval will be:

Narrower for 90% confidence than 95% confidence.

Jamie asks her neighbors as they walk by her when she's walking her dog

convenience sampling

The sample mean from 1 sample is usually a more accurate estimate of the population mean than the center of a sampling distribution.

false

random assignment

generate numbers on a screen and choose

what is the purpose of random assignment?

is a way to measure random selection without any bias create like/similar groups

ratio

level of measurement is the interval level with a natural zero starting point examples are distance, prices, salaries

nominal (qualitative vs quantitiate)

level of measurement that is something that has names, labels, or categories only

A NAPA Auto Parts supplier wants information about how long car owners plan to keep their cars.

mean

We wish to analyze the temperature during summer months for the northeaster part of the US

mean

what is μ?

mean for parameter

N(in PANIC)

name your interval either 1propzint or t-interval

confidence level decreases (95 to 90% confidence), the confidence interval will...

narrower

sample size increases (n get larger), the MOE will get...

smaller

what is the statistic and parameter?

statistic = proportion and parameter = mean

confidence level increase (95 to 99% confidence), the standard error will...

stay same

Rick works for a sports equipment manufacturing company. He separates all the employees into men and women, and then chooses 28 women and 30 men to ask if they want changes to their medical insurance coverage. Identify the method of collecting data

strafied sampling

what is a placebo?

a psychological effect when a person "thinks" he/she got a treatment when it's actually fake. in some cases, believing that they got treatment is a benefit

central limit theorm (CLT)

these are assumptions for proportions and means

Random samples should be at least 30 or nearly normal if we want our random sample means to estimate the population means.

true

The concepts of 95% confidence, confidence intervals, standard error and margin of error can all be better understood from studying sampling distributions.

true

Supposes a sample size of 87 was used to conduct a right tailed hypothesis test for a single population mean. The null hypothesis was H0: m = 45 and the sample mean was 50 and the P-value was 0.03. Then there is a 3% chance that 87 randomly selected individuals from a population with a mean of 45 and the same standard deviation would have a sample mean greater than 50.

True. The p-value is the probability of obtaining a sample mean at least as extreme as the sample mean from the test.

A hypothesis test was used to see if less than 5% of all Americans would still drive to work if gas prices went above $10.00 a gallon. The P-value for this test was 0.03. We can conclude that only 3% of all Americans would still drive to work if gas prices went above $5.00.

False, the p-value is the probability that if the null hypothesis is true and a new sample is taken, then the new sample mean will be at least as extreme as the original one.

You have sampled 25 randomly selected students to find the mean test score. A 95% confidence interval for the mean came out to be between 85 and 92. Which of the following statements gives a valid interpretation of this interval?

If this procedure were to be repeated many times, 95% of the confidence intervals found would contain the true mean score.

When the sample size increases, everything else remaining the same, the width of a confidence interval for a population parameter will:

decrease

The CLT only applies to sample means and does not apply to the distribution of sample percentages.

false

scientists collect evidence by making observations.

true

correlation and causality

you can misinterpret the data to think there is a association with two variables and conclude that one variable causes the other which isn't TRUE

The biologist goes to his 150 favorite hiking places and looks at an acres along each trail

convenience sampling

She obtained an alphabetical list of all the residents in Newhall and numbered them. She then used the computer to generate random numbers to decide which people to question about their voting preferences.

simple random sampling

The biologist enters the 15 million acres into a data base and had a computer randomly select 150 of these acres.

simple random sampling

If the P-value is 0.13 and the level of significance (a) is 0.05 in a hypothesis test for a mean, then we accept the null hypothesis.

False, never accept the null hypothesis when testing for a mean. Instead the conclusion is to fail to reject the null hypothesis.

A quality control specialist at a plate glass factory must estimate the mean clarity rating of a new batch of glass sheets being produced using a sample of 18 sheets of glass. The actual distribution of this batch is unknown, but preliminary investigations show that a normal approximation is reasonable. The specialist decides to use a t-distribution rather than a z-distribution because The z-distribution is not appropriate because the sample size is too small. The sample size is large compared to the population size The t-distribution results in a narrower confidence interval The variability/SD of the population is unknown

The variability/SD of the population is unknown

A researcher wants to test the hypothesis that college students weigh less on average than the average American (160 lbs). The sample mean of the 80 students who were weighed was found to be 142 pounds and the P-value was 0.03. This means that if the mean of all students' weight is 160 lbs, then there would be only a 3% chance that a randomly selected group of 80 students would have a mean weight of less than 142 lbs.

True, the P-value gives that probability that if H0 is true, then the sample mean would less than the sample mean that was found.

If the P-value is 0.003 and the level of significance (a) is 0.05 in a hypothesis test for a mean, then we reject the null hypothesis.

True, when P<alpha, reject the null hypothesis

A researcher hypothesizes that the average student spends less than 20% of their total study time reading the textbook. The appropriate hypothesis test is a left tailed test for a population mean.True. It is left tailed because we are checking if the average is less than 20%. This is a mean and not a proportion, because the variable is quantitative. The survey question would be, what proportion of your study time is spent reading the textbook?

True. It is left tailed because we are checking if the average is less than 20%. This is a mean and not a proportion, because the variable is quantitative. The survey question would be, what proportion of your study time is spent reading the textbook?

A research and development engineer is preparing a report for the board of directors on the battery life of a new cell phone they have produced. At a 95% confidence level, he has found that the battery life is 3.2 ± 1.0 days. He wants to adjust his findings so the margin of error is as small as possible. Which of the following will produce the smallest margin of error? Increase the confidence level to 100%. This will assure that there is no margin of error Increase the confidence level to 99%. Decrease the confidence level to 90%. Take a new sample from the population using the exact same sample size Take a new sample from the population using a smaller sample size.

Decrease the confidence level to 90%.

As the sample size increases, the standard error gets larger

false

The standard error of a sampling distribution is higher than the standard deviation of a single data set.

false

We do not need to study sampling variability, just take some voluntary response data, calculate the sample mean, and then just tell people it is the population mean.

false

what is x bar?

mean for statistic

The music industry must adjust to the growing practice of consumers downloading songs instead of buying CD's. So, it becomes important to estimate the percentage of songs that are currently downloaded.

proportion

what is p?

proportion for parameter

confidence level decreases (95 to 90% confidence), the MOE will get...

smaller

she obtains a list of all residents of Newhall and decides to ask every 50th person on the list.

systematic sampling

The average (center) of all the random sample means will be a good estimate of the population mean.

true

We can approximate the standard error from a sampling distribution without a formula

true

If a researcher wants to test the claim that more than 25% of all students purchased their textbook online, then the null and alternative hypotheses are H0:p=0.25 and Ha:p>0.25.

True, the null hypothesis' operator always contains an = sign and the alternative hypothesis is since the question asks if MORE than 25% of students purchased their textbook.

In a recent survey of 4276 randomly selected households showed that 94% of them had telephones.

proportion

If Alli wants to find out how long it takes her baby sister to fall asleep, she might use the time of day and noise levels as variables in her experiment.

true

In observational study, the researcher relies more on data collected.

true

Random samples will often give very different sample means and sample percentages.

true

population

a group of phenomena that have something in common

what is σ?

standard deviation for parameter

A researcher wishes to estimate amount of money a county spends on road repairs each year.

mean

voluntary response sample

one in which respondents themselves decide whether or not to be included

In a Gallup poll, 1025 randomly selected adults were surveyed and 29% of them said that they used the Internet for shopping at least a few times a year.

proportion

what is p̂?

proportion for statistic

Last year, 30 percent of Americans traveled out of town for their Thanksgiving dinner. A hypothesis test was performed to see if that percent has declined this year (H0: p = 0.30, Ha: p < 0.30). The level of significance of 0.05 was used and the P-value was found to be 0.48. Since P > a, it can be concluded that the percent of Americans who traveled out of Town for Thanksgiving has declined this year.

False. We fail to reject the null as p-value>alpha. So, 30% of American's traveled out of town for Thanksgiving

simple random sample

Find out if the study picked groups of participants. For large numbers of people (like the number of potential draftees in the Vietnam war), it's much easier to pick people by groups (simple random sampling). In the case of the draft, draftees were chosen by birth date, "simplifying" the procedure.

As the confidence level increases the confidence interval will get narrower

false

Calculating standard error is not important in statistics, we only need to look at the regular standard deviation of a single data set.

false

confidence level decreases (95 to 90% confidence), the critical value (z or t) will get ...

smaller

sample size increases (n get larger), the standard error will get...

smaller

If a police officer wants to find out whether the average speed of motorists on a highway with a speed limit of 55 mph is greater than 55 mph,then the null hypothesis is 55.

False, the null hypothesis is: the population mean is 55. The null hypothesis is always a statement, never a number.

A business owner is researching whether the mean amount spent per customer is greater than $40. If the sample size is 18, then as long as the T-statistic is used instead of the Z-statistic, the researcher does not need to assume that the sampling distribution is approximately normal.

False. With a small sample size the normality condition always must be assumed.

A researcher is conducting a study to see if an experimental medication decreases mean cholesterol level. If the sample size is 22, then as long as the T-statistic is used instead of the Z-statistic, the researcher does not need to assume that the distribution is approximately normal

False. With a small sample size the normality condition always must be assumed.

what does double blind mean?

a group of people and even the experimenters are unaware of the outcomes of the experiment. person protoring doesn't know if the administer has placebo or treatment

cluster sampling

divide up population into groups- usually geographically. these groups are called clusters or blocks. the clusters are randomly selected, and each element in the selected clusters are used

A sampling distribution is made up of 1 sample.

false

A small sample size is part of a well-designed experiment

false

Calculating standard error of a sampling distribution is not important, we only need to look at the regular standard deviation of a single data set.

false

Confidence intervals always contain the true population value.

false

In an experiment, the researcher only watches and arrives at a conclusion but does not interfere with the subjects.

false

The sample percentage from just a single data set is usually much closer to the population percentage than the center of a sampling distribution of sample percentages. true or false

false

The standard error of a sampling distribution and the standard deviation of a single data set are the same thing

false

what is the purpose of random selection?

is a way to collect data that allows variability in the outcomes. it helps minimize bias and the sample represents the population

confidence level increases (95 to 99% confidence), MOE will get...

larger

confidence level increases (95 to 99% confidence), the critical value (z or t) will get...

larger

sample sizes decreases (n get smaller) the MOE will get

larger

sample sizes decreases (n get smaller), the confidence interval will be

larger

Do you want to own your own candy store? With some interest in running your own business and a decent credit rating, you can probably get a bank loan on startup cost for franchise such as Candy Express, The Fudge Company, Karamel Korn and Rocky Mountain Chocolate Factory. Startup costs (in thousands) from a random sample of candy stores are given for analyzing.

mean

what does single blind mean?

means when a group of people (experimented on) don't know what they receive when getting a variable. patients don't know if placebo is a treatment

sample size increases (n get larger), the confidence interval will get...

narrower

types of levels of measurement

nominal (qualitative vs quantiative) ordinal data interval ratio population sample parameter statistic voluntary response sample correlation and causality

what is n?

number of members of the sample or population use for statistics and parameter

sample

smaller group of members of a population selected to represent a population usually random

what is s?

standard deviation for statistic

She separates all residents of Newhall in men and women, then chooses 33 men and 29 women to ask ab out their vote

strafied sampling

The biologist orders the 15 million acres by latitude and then surveys every 100,000th acre on the list.

systematic sampling

A fitness center is interested in finding a 90% confidence interval for the mean number of days per week that Americans who are members of a fitness club go to their fitness center. Records of 220 members were looked at and their mean number of visits per week was 2.4 and the standard deviation was 2.1. Round your answers to two decimal places. The sampling distribution follows what kind of distribution?

t distribution

A fitness center is interested in finding a 90% confidence interval for the mean number of days per week that Americans who are members of a fitness club go to their fitness center. Records of 220 members were looked at and their mean number of visits per week was 2.4 and the standard deviation was 2.1. What is the correct Parameter? p = the true proportion of Americans who attend a fitness club \mu = the true proportion of Americans who attend a fitness club the true mean number of days per week that Americans who are members of a fitness club go to their fitness center p = the true mean number of days per week that Americans who are members of a fitness club go to their fitness center

the true mean number of days per week that Americans who are members of a fitness club go to their fitness center

As the confidence level increases the margin of error will increase.

true

Even if a sample is random, the sample value may not be exactly the same as the population value. true or false

true

The distribution of random sample means is normally distributed for sufficiently large samples.

true

The main difference between observational study and experiments is in the way the observation is done.

true

The sample percentage from the center of a sampling distribution of sample percentages is much closer to the actual percentage than from a single data set, usually.

true

convenience sampling

very easy, but the worst technique to use ex: standing out library to ask questions

If it's a random sample, it will always give the same sample values.

false

Random samples will be exactly the same as the population value.

false

If a sample is random, the sample value will be exactly the same as the population value.

false

simple random sample

analogous to putting everyone's name into a hat and drawing out several names. each element in the population has an equal chance of occurring. while this is the preferred way of sampling, it is often difficult to do. it requires that a complete list of every element in the population be obtained. computer generated lists are often used with this

point estimate

center, average

parameter

characteristic of a population

statistics

characteristic of a sample

Jamie randomly selects 45 streets in Newhall and asks every person living on those streets

cluster sampling

The biologist goes to 15 diverse locations that have 10 acres each and surveys all 10 acres for each of these 15 locations.

cluster sampling

Michelle, a teacher at Valencia High, wants to see how many students at Valencia High school will be attending COC. She gives the students in her U.S. History class a questionnaire to fill out that asks where they will be attending college. Identify the method of collecting data (census, simple random sample, systematic, convenience, voluntary response, cluster, stratified).

convenience sampling, voluntary response is incorrect because

stratified sampling

divide the population into groups called strata. however, this time, it is by some characteristic not geographically. for instance, the population might be separated into males and females. a sample is taken from each of these strata using either random, systematic, or convenience sampling

The standard deviation of a single data set and the standard error of a sampling distribution is the same number always.

false

There is human intervention in observations

false

P (in PANIC)

p: state your parameter description on what you're trying to find like the true proportion of egg cartons with at least one broken egg in them

sample size increases (n get larger), the critical value (z or t) will get...

same

sample sizes decreases (n get smaller), the critical value (z or t) will be ..

same

The biologist classifies the Sierras into 10 different ecological types and then makes sure that the proportion of each ecological type from the sample is the same as the proportion of that of the population.

strafied sampling

If a scientist is studying a common type of snail and he or she says that the average length of these snails is 4.5 centimeters, his or her measurements are probably based on a study of more than 15 snails.

true

To create a sampling distribution, take lots of random samples, calculate all their sample means or sample percentages and then make a graph of all the sample means or sample percentages.

true

When the level of confidence and sample standard deviation remain the same, a confidence interval for a population mean based on a sample of n = 100 will be narrower than a confidence interval for a population mean based on a sample of n = 50.

true

C (in PANIC)

write a conclusion

It doesn't matter if the population is skewed, the distribution of sample means will always be bell shaped.

false

Random is not important in the central limit theorem.

false

Suppose a sample size of 103 was used to conduct a left tailed hypothesis test for a single population mean. The null hypothesis was H0: m = 22 and the p-value was 0.04. Then there is a 4% chance that the population mean is equal to 22.

False. The p-value represents the probability that if the null hypothesis is true and another sample is collected, than the new sample mean will be at least as small as the original sample mean.

what is a control group and why is it used?

a group that does not get any alternations base group to compare to experimental group

ordinal data

arranged in some order. they can be ranked, but no mathematical operations are meaningful

systematic sampling

easier than random sampling. the list of elements are counted off and that is every kth element is taken.

A sampling distribution just looks at 1 sample.

false

Random samples should have at least 10 successes and at least 10 failures if we want our random sample percent to estimate the population percent. This means we will always need a data set size of exactly 20.

false

Random samples will be guaranteed close to the population value.

false

The sample percentage from just a single data set is usually much closer to the population percentage than the center of a sampling distribution of sample percentages.

false

As standard deviation increases, samples size _____________ to achieve a specified level of confidence.

increases

Sampling distributions are very useful when studying inferential statistics.

true

The average (center) of all the random sample percentages (proportions) will be a good estimate of the population percent.

true

The COC Admissions department wants to see how many students would be in favor of using a new program to register for classes. They put a link on their website so that any students that want to try out the program can. The students can then take a survey and say how well they like the new system. This is what method of collecting data was used:

voluntary response

non-response bias

when asking a question, people don't respond - be careful - dinner time and someone wants to start a survey no one will answer

A fitness center is interested in finding a 90% confidence interval for the mean number of days per week that Americans who are members of a fitness club go to their fitness center. Records of 220 randomly selected members were looked at and their mean number of visits per week was 2.4 and the standard deviation was 2.1. Were the A --> Assumptions met

yes

I (in PANIC)

interval? t or z test

standard error

standard deviation of the sample

A(in PANIC)

a: state if the sample was random given

interval

can be arranged in order, but with another property: that the difference between any two data values is meaningful scale, quantitative, age of all statistics students, annual income, etc

sample sizes decreases (n get smaller), the standard error will get

larger

confidence level decreases (95 to 90% confidence), the standard error will be...

the same

Random samples will often give very different sample means and sample percentages so they will all have variability.

true

The center of a sampling distribution is usually a more accurate estimate of the population mean than a sample mean from 1 sample.

true

confidence level increases (95 to 99% confidence), the confidence interval will get...

wider

When constructing a confidence interval for a sample proportion, you should use which distribution?

z distribution


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