Question

Researchers randomly assigned 322 moderately obese volunteers to one of three diets to study how the diets compare with respect to various outcomes such as weight loss, lipid profiles, blood pressure, and other indicators of health and metabolic function. The three diets included a low-carbohydrate diet, a low-fat diet, and a Mediterranean diet that consists of moderate fat and a high proportion of monounsaturated fats. All study participants worked at the same research center in Israel, where lunch (the main meal of the day in Israel) was served in a workplace cafeteria, such that at least during the lunch meal, participants were guided toward options that met their diet's guidelines. The researchers found various differences among the different groups, but no striking differences particularly with respect to weight loss. These results led the researchers to conclude that the Mediterranean diet and the low-carbohydrate diet are effective and safe alternatives to a low-fat diet. They suggested that selecting a diet from among these might best be accomplished by considering the individual's lifestyle, preferences, and health needs. Source: Shai, I., Schwarzfuchs, D., Henkin, Y., Shahar, D. R., Witkow, S., Greenberg, I., . . . Stampfer, M. J. (2008). Weight loss with a low-carbohydrate, Mediterranean, or low-fat diet. New England Journal of Medicine, 359, 229-241.] One limitation cited by the authors of this study is that these researchers had an unusual opportunity to make sure each participant's main meal matched their assigned diet's guidelines. The results might be less applicable to the population of all moderately obese individuals, including those who are not served specially tailored meals in the workplace. Suppose you are a bariatric researcher conducting a similar study among a random sample of moderately obese volunteers in the United States. You randomly assign your volunteers to one of the same three diets, and you provide your volunteers with nutritional counseling but no specially prepared meals. You are particularly interested in differences between the three diets with respect to the decrease in the average number of calories consumed per day. You use a statistical computing package, such as SPSS®, to conduct a single-factor, independent-measures ANOVA. The table that follows shows the data in stacked format from the first five study participants. The column labeled CALORIES_DEC" is each participant's decrease in calories consumed in calories. The column labeled "DIET" describe:s which diet each participant followed, where 1 low carbohydrate, 2 low fat, and 3Mediterranean. IDNUM CALORIES DEC DIET 001 002 003 004 005 201 659 452 211 56 2 2 When setting up your analysis, you place the variable in the Factor box. You place the variable in the Dependent List box. Descriptives CALORIES_DEC 95% Confidence Interval for Mean Mean 377.64 576.21 453.45 466.12 Std Deviation 413.53 231.24 244.73 319.63 Std Error 61.6454 36.1136 37.7627 28.252 Lower Bound 373.75 573.93 451.07 466.0568 Upper Bound 381.53 578.49 455.83 466.1824 1.00 2.00 3.00 Total 45 41 42 128 ANOVA Sum of Squaresdf Mean Square 427973.16 96950.33 Sig 855,946.31 12,118,791.87 12,974,738.18 4.41 Between Groups Within Groups Total 2 125 127 0.0141 The two prior tables consist of the output of the statistical computing package. Considering these results, fill in the blanks in the following statement that describes the results in APA format. Assume that your chosen significance level is a - .05. (Note: These results are hypothetical.) The two prior tables consist of the output of the statistical computing package. Considering these results, fill in the blanks in the following statement that describes the results in APA format. Assume that your chosen significance level is α = .05. (Note: These results are hypothetical.) The means and standard deviations are presented in Table 1. The analysis of variance indicates that there significant differences among the three diets, F , and η TABLE 1 The decrease in the average number of calories consumed per day Low-Carbohydrate Diet Low-Fat Diet Mediterranean Diet SD

Answer 1

you place the variable Diet in factor box

You place the Calories_Dec in dependent list box

There is significant difference

F(2,125) = 4.41 ,

p = 0.0141

n^2 = 855946.31/12974738.18

= 0.065970