1- A study is conducted to determine whether people learn better with spaced or

Question

1-A study is conducted to determine whether people learn better with spaced or masse practice. Subjects volunteer from an introductory psychology class. At the beginning of the semester 12 subjects volunteer and are assigned to the massed-practice condition. At the end of the semester 12 subjects volunteer and are assigned to the spaced-practice condition. This experiment involves two kinds of non-random sampling: (1) Subjects are not randomly sampled from some specified population and (2) subjects are not randomly assigned to conditions. Which of the problems relates to the generality of the results? Which of the problems relates to the validity of the results? Which problem is more serious?

2- Name some ways to graph quantitative variables and Some ways to graph qualitative variables.

3-You have to decide between displaying your data with a histogram or with a stem and leaf display. What factor(s) would affect your choice?

4-A student has decided to display the results of his project on the number of hours people in various countries slept per night. He compared the sleeping patterns of people from the US, Brazil, France, Turkey, China, Egypt, Canada, Norway, and Spain. He was planning on using a line graph to display this data. Is a line graph appropriate? What might be a better choice for a graph?

5-A graph appears below showing the number of adults and children who prefer each type of soda. There were 130 adults and kids surveyed. Discuss some ways in which the graph below could be improved?

Explanation / Answer

1)

Given:

a. Subjects are not randomly sampled from some specified population and

b. Subjects are not randomly assigned to conditions.

Which of the problems relates to the generality of the results?

The results can be generalized only if the study samples are from specified population. For example, if a new a drug is invented for child with the age of 1-2 years. Then the study sample for test the ability of the new drug should include subjects randomly seleceted from children with the age group of 1-2.

Since, Subjects are not randomly sampled from some specified population we can't be able to generalize the results

Which of the problems relates to the validity of the results?

The results will be valid only if the subjects are randomly to the treatment. Becuase, if the subjects are randomly assigned to the treatment we can expect that every one has equal chance of getting the treatment and the baseline characteristic of the study population will be balance. Else, the results will be biased due to the study population. So, subjects are not randomly assigned to conditions will be the problem for validity of the results.

Which problem is more serious?

Both the problems are serious. But still to generalize the results, the results from the experiment should be valid. Hence, the problems relates to the validity of the results is more serious.

2) Name some ways to graph quantitative variables and Some ways to graph qualitative variables.

Quantitative variables:

Histogram - To assess the distribution of the quantitative variable

Box plot - To check the descriptive statistics

Error bar plot - To show the dispersion of the variable

Qualitative variable:

Pie chart - To show the frequency distribution of the variable

Bar chart - To show the frequency distribution of the one or more variables with one or more bars in the graph

3) You have to decide between displaying your data with a histogram or with a stem and leaf display. What factor(s) would affect your choice?

Stem and leaf:

Stem and leaf display will be the more useful graph to display the distribution of particulare variable. Because, from the stem and leaf graph we can also be able to retrive the raw data.

4) Number of hours people in various countries slept per night:

A variable of the interset for the student is number of hours people in various countries slept per night whihc is a quantitative variable. Hence, the appropriate descriptive statistics which can be used for the variable will be mean and standard deviation. Line graph will not be appropriate to display the mean number of hours. Because, line graph can be used if the data is compared over a period of time. As, the number of hours compared here is between the countries, box-plot with boxes for each country will be more appropriate.

5. Improvement in the given bar plot:

The graph given is plotted for frequencies between the different preferred soda between adults and kids. Instead of frequencies, if the plot is given for percentages for each preferred soda it would have been more informative.

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