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Description
Flashcards by Krisha Johnson, updated more than 1 year ago
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Created by Krisha Johnson
about 8 years ago
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| Question | Answer |
| What are the three characteristics of the normal distribution? | 1. The normal distribution is bell-shaped and symmetrical. (Mean = Median = Mode) 2. It can be described by two parameters: the mean and the variance (remember the variance is just the standard deviation squared). 3. The tails are asymptomatic. This means that the tails of the distribution go on for infinity and they never touch the X-axis. |
| What is the mean and variance of the standard normal distribution? | The mean is 0 with a standard deviation of 1. |
| What do z-scores tell us? | Z-scores tell us how many standard deviations above or below a mean a particular value is |
| Is a parameter considered to be a constant or a random variable? Is a statistic considered to be a constant or a random variable? | There is only one population parameter (e.g., there is only 1 mean for the population) so it is constant (i.e., it never changes). However, we can have many different samples and the sample statistics (e.g., means) can vary - so sample statistics (means) are considered to be a random variable. |
| What is a sampling distribution of the sample mean? | A sampling distribution of a sample mean is a frequency distribution of sample means (i.e., it’s a histogram displaying the frequencies of different values of sample means). |
| What is the standard error and what does it tell us? | The standard error is the standard deviation of the sampling distribution. It tells us the average difference between a sample mean and a population mean. |
| How does the sample size effect the standard error? | The sample size influences the size of the standard error. If you increase the sample size, you will decrease the size of the standard error. Remember, the standard error is how much we expect our sample mean to differ from the population mean. That means, if you increase the sample size, the sample mean will be closer or more similar to the population mean. |
| What are the two main tenets of the central limit theorem? | 1. It tells us what the mean and standard deviation of the sampling distribution of the sample mean is. The mean of the sampling distribution of the sample mean equals the population mean. This means that the average sample mean is the same as the population mean. The standard deviation of the sampling distribution (AKA standard error) is the population standard deviation divided by the square root of the sample size. 2. The distribution of the sample means (AKA the sampling distribution) will be normal if the sample size is 30 or greater. |
| What is the null hypothesis? | The null hypothesis is the hypothesis of no relationship between the IV and the DV. It states that there will be no differences between the two groups (i.e., the two groups will have the same mean) |
| What is an alternative hypothesis? | The alternative hypothesis is the research hypothesis. It’s what the researcher is expecting, or hoping, to find. The alternative hypothesis states that there is a difference between the two groups (2-tailed) or that one group is greater or less than the other group (1-tailed). |
| Is the null and alternative hypothesis about the sample or the population? | The null and alternative hypothesis are about the population. They are expectations about populations. However, we use samples to test the hypothesis. (Hypothesis testing = inferential statistics) |
| Fill in the blank: Inferential statistics use _______ to draw conclusions about _______ | Samples, Populations |
| Do the following terms refer to the same concept (Yes or No)? Standard deviation of the sampling distribution, standard error, sampling error. | Yes. All three terms refer to the same thing. |
| Independent Variable (IV) | What the research is about - we're interested in effects of the IV May be quantitative or qualitative |
| Dependent Variable (DV) | Is hypothesized to be influenced by the IV Often quantitative (but can be qualitative) |
| Mnemonic Device | The IV influences / has an effect on the DV (plug into sentence) The DV is dependent on the IV |
| Two-tailed test | the goal of research is to just show that two populations are different |
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