statistics test #2 revised
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
