Monthly Archives: February 2016

Central Limit Problems Using Sample Proportions

This video covers word problems requiring the sample proportions versions of the Central Limit Theorem formulas. These problems always start by giving you the percentage of a population that has a certain characteristic, then ask you the probability that the proportion of a random sample will be either greater or less than that of population at large. Z-values and calculator, hear we come!

This video appears on the page: Sampling Means & Sampling Proportions Example

Central Limit Problems Using Sample Means

This video covers how to do Central Limit Problems which require the sampling mean approach. These are the problems that give you the mean and standard deviation of some population, then ask you the probability that the mean of a random sample will be either more or less than that. Z-values and calculator, hear we come!

This video appears on the page: Sampling Means & Sampling Proportions Example

Sample Mean vs Sample Proportion: When To Use Which

This video teaches you to spot which Central Limit Theorem problems should be approached using sample means and the related formulas, versus which problems require the sample proportions approach.

This video appears on the page: Sampling Means & Sampling Proportions Example

Central Limit Theorem Examples:
Sampling Means & Sampling Proportions
Sample Mean vs Sample Proportion: When To Use Which
Central Limit Problems Using Sample Means
Central Limit Problems Using Sample Proportions

In the previous chapter we took a look at the Central Limit Theorem from a more theoretical viewpoint, looking at distrubutions of p-hats and x-bars. Now we'll get into doing lots of examples of the two types of word problems that use the CLT: they give you a population's mean and standard deviation or proportion, then ask you the probability that a random sample would have a certain average or proportion.

Part of the course(s): Statistics

Rules for Central Limit Theorem

This short video explains the "criteria" for when you're allowed to use the central limit theorem. Not that you'd care, except that's often the first step of test and AP questions.

This video appears on the page: Central Limit Theorem

Intro to Central Limit Theorem

This video explains what the central limit is, and outlines how you'll be using it to solve big fancy word problems. It also shows you where that graph comes from that's in every book and lecture on the topic: a pile of sample variances, x-bars and p-hats stacked up in the shape of a normal distribution.

This video appears on the page: Central Limit Theorem

Central Limit Theorem
Intro to Central Limit Theorem
Rules for Central Limit Theorem

This chapter tells you what the central limit theorem says, shows you how to draw those little distributions with all the x-bars and p-hats piled up into normal distributions, and explains the rules to when you're allowed to use this thing. The problems you can do with this thing come in the next chapter.

Part of the course(s): Statistics

Finite Population Adjustment for Standard Error

Usually when you're working with sampling distributions, you assume that the population (N) is very large compared to the sample size (n). But sometimes you'll see problems where they tell you the population size, and it's small, so keep an eye out because you'll need to "adjust" the standard error with the formula in the thumbnail.

This video appears on the page: Sampling Distributions—xbar, phat

Standard Error

This is that symbol that looks like it should be called the "standard deviation of the distribution of sample means which you use to find the z-value of a sample mean relative to its sampling distribution of the means." Maybe "standard error" was just shorter?

This video appears on the page: Sampling Distributions—xbar, phat

Sampling Distribution Vocab

This video goes through all the symbols you can see in the thumbnail to the right -- phat (pronounced pee-hat), standard error, etc -- explaining what they mean and also what they're called, to help you figure out what terms to look for to find more videos about each one.

This video appears on the page: Sampling Distributions—xbar, phat

Sampling Distribution vs Sample Distribution

This video explains what a sampling distribution is (distribution of sample means and variances), how it's different from a sample distribution (without the -ing), and gives you a taste of what the central limit theorem is going to be all about.

This video appears on the page: Sampling Distributions—xbar, phat

Sampling Distributions (x-bar, p-hat),
Distribution Of The Sample Mean:
Sampling Distribution vs Sample Distribution
Sampling Distribution Vocab
Standard Error
Finite Population Adjustment for Standard Error

These videos cover sampling distributions of the mean and proportion, also known as the "distribution of the sample mean" and "distribution of the sample proportion." Lots of examples and vocab, including p-hat (phat), so that you'll be ready for the central limit theorem.

Part of the course(s): Statistics

Exponential Probability Distributions (Continuous)

This chapter covers a type of distribution that many classes don't cover -- exponential distributions -- which tells you the chances of an event happening in the immediate future. For example, if someone walks into Starbucks every 2 minutes on average, what are chances of someone walking in within the next 1 minute.

Part of the course(s): Statistics

Exponential Probability Distributions (Continuous)

This video covers a type of distribution that many classes don't cover -- exponential distributions -- which tells you the chances of an event happening in the immediate future. For example, if someone walks into Starbucks every 2 minutes on average, what are chances of someone walking in within the next 1 minute.

This video appears on the page: Exponential Probability Distributions (Continuous)

Z-Score Table Calculations On Your Calculator

This video covers how to use your calculator to replace the z-score table that's in your book. If you don't get to use a calculator on the test, that's obviously not going to help you, but many z-table problems can be done just on your TI-84.

This video appears on the page: Calculating Probability Using Z-Score & Normal Distribution

How To Use Z-Score Table To Calculate Probability & Proportion

Now that we've covered the basics of this type of problem in the preceding videos, we're finally ready for 30 minutes of awesome examples which will make you the master of transforming x's to z's and back again!

This video appears on the page: Calculating Probability Using Z-Score & Normal Distribution

Z-Scores In Reverse-Calculating Cutoffs From A Probability

Once you already know how to do the crazy z-score table problems in the previous video, this video covers a particularly over-the-top version of those problems: instead of giving you a cutoff x and asking you for the percentage above or below that value, they give you a percentile and ask for the cutoff x value. Pretty crazy.

This video appears on the page: Calculating Probability Using Z-Score & Normal Distribution

How To Read A Z-Score Table

This video shows you how to use those z-score tables which give you the "area to the left" of a z-value. They can be a bit confusing when you first see them, plus there's some wacky stuff going on around zero.

This video appears on the page: Calculating Probability Using Z-Score & Normal Distribution

How To Spot Z-Score Table Problems

Before you can do a z-score table problem, you've got to know what they look like. So this video gives you everything you'll need to know to spot these puppies on the test, from the easy ones to the most crazy one I've ever seen.

This video appears on the page: Calculating Probability Using Z-Score & Normal Distribution

The Normal Distribution: Calculating Probability Using Z-Score:
Calculating Z-Score
How To Spot Z-Score Table Problems
How To Read A Z-Score Table
How To Use Z-Score Table To Calculate Probability & Proportion
Z-Scores In Reverse-Calculating Cutoffs From A Probability
Z-Score Table Calculations On Your Calculator

These videos cover all those crazy word problems where they give you the mean and standard deviation of a population, then ask you what percentage of that population is shorter or taller or heavier or lighter than some cutoff value. That's what the normal distribution is all about. And of course we'll also cover how to do all this on your calculator.

Part of the course(s): Statistics