# Web Activities

Click on the following links. Please note these will open in a new window.

#### Comparing a distribution of scores to a distribution of means I

Go to this following website: http://onlinestatbook.com/2/calculators/normal_dist.html

The following website has a z-distribution that allows you to see the area under the curve as you change different parameters--we used this same calculator in Chapter 4, but it can be used for distributions of means as long as you use the standard error where it says “SD” (because the standard error is the SD of the distribution of means). Remember the distribution of typical IQ scores (m = 100; s = 15)? Use those parameters, but now assume that you will randomly sample nine people from the population. First, determine the standard error of the mean (σm = ?). Now, use the buttons below to examine the shaded area and the exact probability that the mean IQ for 25 individuals (n = 9), randomly selected from the population, will be: (1) Above 115, (2) Below 90, (3) between 90 and 100, and (4) outside of 95 and 105. Report the answer for each value. Now, change each of the values above and see how it changes the area-under-the-curve.

#### Comparing a distribution of scores to a distribution of means II

Go to the following website: http://davidmlane.com/hyperstat/z_table.html

The following website has a z-distribution that allows you to see the raw scores as you change different parameters. Again, we used this same calculator in Chapter 4, but it can be used for distributions of means as long as you use the standard error where it says “SD” (because the standard error is the SD of the distribution of means). Let’s take a look at the distribution of typical IQ scores (m = 100; s = 115). First, click on “Values from an Area (Use to compute Z for confidence intervals)” button. First, determine the standard error of the mean (σm = ?). Now, use the buttons below to examine the shaded area and the raw scores for each of the areas p = .05 (above and below). Next, use the buttons below to examine the shaded area and the raw scores for each of the areas p = .95 (between and outside). Report the answer for each value. Now, change each of the values above and see how it changes the raw scores.

#### How much will you need to spend to buy a new car?

Go to your favorite search engine and search for the average Big Five personality traits of adults (you will need to also find the standard deviations). Personality is known to increase and decrease with age (e.g., younger people tend more neurotic and less conscientious.). Find the average personality traits for a few different age groups. With this information, create an expected distribution of means (from –3 to 3 standard errors) on various personality traits when you sample 36 people from specific age groups.