The following are 32 reaction times on a scale of 0 to 260 ms: 201, 202, 205, 205, 207, 208, 208, 209, 209, 210, 211, 213, 215, 215, 217, 218, 222, 224, 225, 227, 229, 229, 231, 235, 236, 238, 243, 248, 249, 249, 253, 253 a. Create a grouped frequency table with six class intervals using interval widths of ten. Where you need to round keep two decimal places for percent and four decimal places for proportions. Show all calculations where applicable. X F P % Cumulative % b. Present the data using a graph that is appropriate for this variable. Use the same class intervals and be sure to label both the x-axis and the y-axis. This can be hand drawn. c. What is the shape of the distribution?
Inverse Normal Distribution
The method used for finding the corresponding z-critical value in a normal distribution using the known probability is said to be an inverse normal distribution. The inverse normal distribution is a continuous probability distribution with a family of two parameters.
Mean, Median, Mode
It is a descriptive summary of a data set. It can be defined by using some of the measures. The central tendencies do not provide information regarding individual data from the dataset. However, they give a summary of the data set. The central tendency or measure of central tendency is a central or typical value for a probability distribution.
Z-Scores
A z-score is a unit of measurement used in statistics to describe the position of a raw score in terms of its distance from the mean, measured with reference to standard deviation from the mean. Z-scores are useful in statistics because they allow comparison between two scores that belong to different normal distributions.
The following are 32 reaction times on a scale of 0 to 260 ms:
201, 202, 205, 205, 207, 208, 208, 209, 209, 210, 211, 213, 215, 215, 217, 218, 222, 224, 225, 227, 229, 229, 231, 235, 236, 238, 243, 248, 249, 249, 253, 253
a. Create a grouped frequency table with six class intervals using interval widths of ten. Where you need to round keep two decimal places for percent and four decimal places for proportions. Show all calculations where applicable.
| X | F | P | % | Cumulative % |
b. Present the data using a graph that is appropriate for this variable. Use the same class intervals and be sure to label both the x-axis and the y-axis. This can be hand drawn.
c. What is the shape of the distribution?
a)
- A frequency distribution is the type of table format that is used to display the frequency of either certain scores or how often scores occur in a class interval.
- The frequency corresponding to each class interval represents the number of scores that fall within the specified interval.
- For computing the relative frequency or proportion of each class, divide the frequency of that class by the sum of total frequencies.
- A percentage distribution is obtained by multiplying the relative frequency of each class by .
- Compute the cumulative percentage frequency corresponding to each class interval by adding all the percentages up to that specific class such that the cumulative percentage for the last class will always be and the cumulative percentage for the first class will always be the same as the corresponding percentage frequency of that class.
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