All AP Statistics Resources
Example Questions
Example Question #1 : Independent Random Variable Combination
A dice is rolled five times in a row. Each time, a 6 is rolled. What is the probability that a 6 will be rolled on the sixth roll? Assume that the dice is fair and has six sides.
The answer cannot be determined with the information given.
Regardless of the previous results of the dice rolls, the probability of each individual dice roll remains the same. Each time the dice is rolled, there is a 1/6 chance that it will land on a specific number. Therefore, there is a 1/6 chance that the dice will roll a 6 on the sixth roll.
Example Question #2 : Dependence And Independence
A coin is tossed 100 times and each time, the coin lands on tails. What is the expected probability of the coin landing on tails if it is rolled an infinite number of times? Assume that the coin is fair and has two sides - heads and tails.
According to the Law of Large Numbers, the probability of the coin landing on tails after being rolled an infinite number of times is equal to the probability of the coin landing on tails in an individual roll: 50%.
Example Question #5 : Dependence And Independence
A student is conducting different experiments that include the rain fall totals in his town, the change in temperature, the tidal levels on the beach, and the humidity. These will all be measured over the next couple of months to figure out the current trends. What would the independent event be in these experiments?
Rain fall in inches
Humudiity percentage
Temperature in degrees
Time in hours
Tidal levels in feet
Time in hours
Time is the independent variable as time is not affected by the other variables but the other variables all change as time lapses.
Example Question #192 : Ap Statistics
Which of the following represents a continuous variable?
The concentration of DNA in a liquid sample.
The weight of footballs.
Two of these.
None of these.
The number of fish in aquariums.
Two of these.
A continuous variable may assume an infinite number of different values between two given points while a discrete variable may only assume a specific number of specific values between two given points. Given this information, it becomes apparent that the concentration of DNA in a liquid sample and the weight of footballs are both continuous variables.
Example Question #1 : Independent Random Variable Combination
A hair care company is testing a new shampoo formula for its ability to keep hair clean for longer thanks to a new chemical compound XYZ that should limit oil production.
To test the appropriate strength of the shampoo, they are testing several concentrations of chemical XYZ to and measuring the amount of oil on the participant's scalp after 24 hours. The color of the shampoo will be randomly changed to keep the participants from knowing what shampoo is which strength.
Which of the following is the Dependant variable?
Length of Participant Hair
Shampoo Color
Amount of Oil on Participant's Scalp
Concentration of Chemical XYZ in shampoo
Gender
Amount of Oil on Participant's Scalp
The Independent variable is what the experimenters are directly manipulating-- here, that is the strength of the Chemical XYZ.
The Dependent variable is the variable that changes based on the Independent variable-- in this case, it is the amount of oil on participants' scalps.
Example Question #193 : Ap Statistics
A group of student researchers want to test the impact of temperature and lighting on the amount of food laboratory rats will eat.
To do this, they will first vary the room temperature (Hot or Cold) and see how much the lab rats eat at each temperature.
They will then vary the lighting (On or Off) and see how much the lab rats eat during each lighting state.
Which of the following is the Dependant Variable?
Room Temperature
Mouse Food Intake
Room Lighting
The number of rats
None of the other answers
Mouse Food Intake
A Dependent variable is what changes based on the independent, manipulated variable.
The Independent variables are the Room Temperature and the Lighting state, which the researchers were manipulating themselves.
The Dependent variable is the Mouse Food Intake, which is the variable that changed based on how the independent variables changed.
Example Question #194 : Ap Statistics
If is a random variable with a mean of and standard deviation of , what is the mean and standard deviation of ?
Remember how the mean and standard deviation of a random variable are affected when it is multiplied by a constant.
Example Question #195 : Ap Statistics
If you have ten independent random variables , normally distributed with mean and variance , what is the distribution of the average of the random variables,
Normal distribution with mean and variance .
Normal distribution with with mean and variance .
Chi-square distribution with degrees of freedom.
Normal distribution with mean and variance .
Normal distribution with with mean and variance .
Any linear combination of independent random variables is also normally distributed with the mean and variance depending on the weights on the random variables. The mean is additive in the sense that
Each is , so the sum is equal to zero.
This means the sum of the average
is .
The variance satisfies
because of independence.
This means that the average is normally distributed with mean and variance .
Example Question #196 : Ap Statistics
Suppose you have three independent normally distributed random variables, , such that
has mean and variance ,
has mean and variance ,
has mean and variance .
What is the probability that the sum, , is less than ?
There is a relatively simple way of doing this problem. The sum of any set of independent normal random variables is also distributed normally. So has a normal distribution. Now we can compute the mean and variance. The mean is additive:
Variance is also additive in some sense, when the random variables are independent:
Thus, is normally distributed with mean and variance .
This sum is a standard normal distribution.
The chance that is thus , if we use a normal table.
Example Question #1 : How To Find The Mean Of The Sum Of Independent Random Variables
An experiment is conducted on the watermelons that were grown on a small farm. They want to compare the average weight of the melons grown this year to the average weight of last year's melons. Find the mean of this year's watermelons using the following weights:
To find the mean you sum up all of your values then divide by the total amount of values. The total sum of the weights is and there are 10 melons.
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