Numerous studies suggest that prenatal alcohol exposure affects gross motor development in young children, particularly when the exposure is moderate to heavy (Lucas et al., 2014). Imagine that you want to replicate these studies. You identified a sample of 33 infants, age 24 months, who had been exposed to moderate levels of alcohol prenatally and determined their level of motor development, using the Bayley Scales of Infant and Toddler Development, Third Edition (Bayley III). This test has a mean () of 100 and standard deviation () of 15. Use these as your population mean and standard deviation. The scores of your sample are listed below. (These scores are fictional.) Using a single-sample z test (Z-Test Calculator for a Single Sample) from the online statistical calculator found at socscistatistics.com, calculate a z statistic to determine whether the scores of the toddlers in your sample differ from average.

Click on the box that says "Yes, calculate the sample mean from raw values." Then copy and paste the raw scores below into the box on the online calculator. (Be sure to scroll down to the bottom of the list of scores so you will include all 33 scores.) Use a two-tailed test with an alpha of .05. Note that the online calculator asks for the population variance (²), rather than standard deviation (), so you have to square the standard deviation reported above. (Observant students will notice that the online calculator uses the following formula for calculating standard error: S_M= ²/N. This works out the same as the formula given in the notes: /N, so please do not concern yourself with this.)

Be sure to answer the questions that follow. Take a screenshot of the online calculations and paste it to the bottom of your assignment page. You can use the Snip function on your calculator (Windows icon, Shift, S). Alternatively, you can use the Print Scrn button and use Ctrl P to paste the image, or any other method to produce a copy of the screen.

Scores (Please scroll down to the bottom of the list on the next page.)

102

92

85

115

92

98

85

85

72

87

115

95

100

90

96

100

88

79

92

98

105

98

87

105

87

99

102

100

85

95

79

85

85

Research hypothesis: Moderate levels of prenatal alcohol exposure affect motor development of toddlers.

Null hypothesis: Moderate levels of prenatal alcohol exposure do not affect motor development of toddlers.

Answer the following questions:

1. Looking at the research and null hypotheses as stated above, what is the independent variable?

1. Looking at the research and null hypotheses as stated above, what is the dependent variable?

1. What is the calculated value of the z statistic?

1. What is the p-value associated with this result?

1. Is the result statistically significant at the .05 level?

1. Do you reject the null hypothesis at the .05 level?

1. Repeat the calculation using the .01 level of significance. Is the result statistically significant at this level?

1. Do you reject the null hypothesis at the .01 level?

1. What is your conclusion?

Paste (Ctrl V) the image of the results from soscistatics.com here: