Stats Help for College-level Students

Random Variables - Combining and transforming

Let X and Y have the joint pdf f x,y(x,y) = 4e^-x-4y for x>0 and y>0. Define Z=X+Y. Find fz(z).

z value

The standard IQ test has a mean of 100 with a standard deviation of 10. Find the z value corresponding to a score of 120. a. 2.79 b. 2.0 c. -2.79 d. -2.0

Intro to Statistics Question

what kind of test is used if the population standard deviation is not known and is less than 30?

Confidence Interval

Which of the following is not needed to be known to calculate a confidence interval? a. standard deviation b. sample size c. mean d. degree of confidence

Statistics Question

When computing confidence intervals for variances and standard deviations, what assumption must be made? a. the variable must be normally distiributed b. the variable must positively skewed c. the variable must be negatively skewed d. none of the above

When does a type I error occur?

When does a type I error occur? a. when the null hypothesis is accepted and it is false b. when the null hypothesis is rejected and it is true c. when the hypothesis is completely disregarded d. none of the above

test value

A liberal arts college has a mean grade point average of 2.45 with a standard deviation of .69. The dean of the psychology department believes that his students have a higher grade point average than the mean of the college. Find the test value. a. 2.502 b. 1.296 c. 1.968 d. 3.194

Intro to Statistics Question

The two different formulas for the t test are for which two different types of problems? a. the samples are dependent or the samples are independent b. the variances are assumed to be equal or unequal c. the samples are both large or both small d. the populations are normally distributed or skewed

Dependent Samples

Which test should be used if the samples are dependent? a. z test b. t test c. t test for differences d. z test for proportions

The mean price of 7 Hewlett Packard computers is $815 with a standard deviation of $19.

The mean price of 7 Hewlett Packard computers is $815 with a standard deviation of $19. The mean price of 9 IBM computers is $845 with a standard deviation of $9. If the alpha value is 0.05, can a computer shopper conclude that the IBM computers cost more? a. yes, there is enough evidence to conclude IBM computers cost more ...continues