Z-score for a random variable
For a standard normal distribution, find:P(z < 1.51)
0.9345
What is a confidence interval?
A range of values that a parameter falls within specified to a certain level of confidence
Assuming a normal distribution, as the standard deviation increases, the shape of curve
becomes shorter and wider
Test the claim that the proportion of people who own dogs is larger than 20% at the 0.01 significance level. The null and alternative hypothesis would be:
Null Hypothesis:p≤0.2
Alternative Hypothesis: p>0.2
Suppose that KC financial aid allots a textbook stipend by claiming that the average textbook at KC bookstore costs $ 96.93. You want to test this claim. The null and alternative hypothesis in symbols would be:
Null Hypothesis:μ=96.93
Alternative Hpyothesis:μ≠96.93.
For a standard normal distribution, find:P(z > -1.89)
0.9706
What happens to a confidence interval if the sample size increases?
The width of the overall confidence interval decreases.
As the standard deviation of a normal curve decreases, the data becomes __________ centered around the mean.
More
Test the claim that the proportion of people who own cats is larger than 20% at the 0.10 significance level. The test is:
Right tailed
Test the claim that the mean GPA of night students is larger than 5.5 at the 0.10 significance level. The test is:
Right tailed.
Adult men have heights with a mean of 69.0 inches and a standard deviation of 2.8 inches. Find the z-score of a man 74.5 inches tall. (To 2 decimal places)
1.96
How can one calculate each tail of a confidence interval?
By first finding the margin of error for a distribution we can then calculate each end of the interval by adding and subtracting it from the mean
When sampling and the standard deviation is not known, what is used to estimate it?
the standard deviation of the data from the sample
"Trident" bubble-gum company claims that 7 out of 10 people prefer their gum to "Orbit". Test their claim at the 90-confidence level. The null hypothesis in words would be:
The proportion of all people that prefer Trident gum is 0.7.
Suppose that KC financial aid allots a textbook stipend by claiming that the average textbook at KC bookstore costs $ 100.00. You want to test this claim. The null hypothesis in words would be:
The average price of all textbooks from the store is $100.00.
On a nationwide math test, the mean was 66 and the standard deviation was 10. If Roberto scored 80, what was his z-score? (To 2 decimal places)
1.40
In order to increase the width of a confidence interval should one increase or decrease the level of confidence?
Increase
If a z-score is equal to zero, which of the following must be true?
The x-value must be equal to the mean of the distribution.
Test the claim that the proportion of people who own cats is larger than 10% at the 0.01 significance level. Based on a sample of 600 people, 17% owned cats. The p-value is 0.00. Based on this we:
Reject the null hypothesis. (B/c LOS > P-value)
Test the claim that the mean GPA of night students is larger than 3.4 at the 0.10 significance level. Based on a sample of 35 people, the sample mean GPA was 3.42 with a sample standard deviation of 0.04. The p-value is:0.00. Based on this we:
Reject the null hypothesis (B/c LOS > P-value)
For a standard normal distribution, find:P(-0.9 < z < 0.95)
0.6449
What does a 95% confidence level mean?
It means we can be up to 95% certain that our data will fall between the specified parameters
Which is greater in a normal distribution, the mean or the median? Explain.
Neither; the mean and median are always equal in a normal distribution, since it is symmetric.
Test the claim that the proportion of people who own cats is smaller than 10% at the 0.005 significance level. Based on a sample of 800 people, 4% owned cats. Based on this we:
Reject the null hypothesis. (B/c LOS > P-value)
Test the claim that the mean GPA of night students is significantly different than 2.9 at the 0.1 significance level. Based on a sample of 55 people, the sample mean GPA was 2.92 with a sample standard deviation of 0.04. Based on this we:
Reject the null hypothesis (B/c LOS > P-value)