Collection and Organization of Data.pptx

Collection and Organization of Data

1. COLLECTION OF DATA Data are collected from different sectors such as business, education, medicine, etc. Collection of data is an important part of statistics. Data should be collected in a manner that they are accurate and convenient to use.

2. Data are collection of facts or information. They may be gathered by using the following methods: Conducting surveys Observing the outcomes of events Taking measurements in experiments Reading statistical publications

3. COLLECTION OF DATA The interview method and questionnaire method can be used in conducting surveys. The interview method is done when a person solicits information from another person. The person gathering the data is called interviewer , while the person supplying the data is the interviewee .

4. COLLECTION OF DATA Behavioral scientists are primarily concerned with the behavior of an individual or a group of individuals. The data are gathered either individually or collectively by means of observation. The person who gathers the data is called an investigator while the person being observed is called the subject .

5. Mrs. Rivera wants to find the number of students in her advisory class who has birthdays falling on each of the 12 months. She collects the data in the following manner: Check the date of birth each student in the class registry Ask the students to raise their hands if their birthdays fall in a certain month Make a form and ask the students to write their birthdates and return the form to her

6. The following data are obtained in a survey on the number of cellphones possessed by each family. How many families were surveyed? How many families have at least two cellphones in their possession? How many families have less than four cellphones? 3 4 5 4 3 4 1 6 5 2 4 5 2 3 6 3 3 2 1 3 2 3 4 5 3 2 4 3 4 5 4 2 5 3 4 6 3 5 3 6 1 3 4 2 3 4 2 4 6 3

7. FREQUENCY DISTRIBUTION TABLE The data collected are called raw data . These data are collected in a survey. We can hardly see any pattern in any set of raw data. Hence, we have to organize the data using a table by following the given steps. The table formed is called a frequency distribution table. A frequency table shows a clear and definite information about a set of data.

8. STEP 1. Set up table using three columns. Number of Cellphones Tally Frequency 1 2 3 4 5 6 Total

9. STEP 2. Read each item in the raw data and mark a stroke (or tally) in the Tally column in the same row as its class. Number of Cellphones Tally Frequency 1 lll 2 IIII III 3 IIII IIII IIII 4 IIII IIII II 5 IIII II 6 IIII Total

10. STEP 3. The frequency of the class is the number of times each class occurs. Write down the frequency of each class by counting the corresponding tally marks. Find the sum of all frequencies and write it as shown. Number of Cellphones Tally Frequency 1 lll 3 2 IIII III 8 3 IIII IIII IIII 15 4 IIII IIII II 12 5 IIII II 7 6 IIII 5 Total 50

11. GROUPED FREQUENCY DISTRIBUTION Step 1. Get the difference between the highest score and the lowest score. Add 1 to the difference to arrive at the total number of scores or potential scores. The difference between the highest score and the lowest score is called the range . Range = Highest Score – Lowest Score Total number of Potential Scores = Range + 1

12. GROUPED FREQUENCY DISTRIBUTION Step 2. Decide on the number of class intervals which is appropriate to the given set of data. Divide the final number in Step 1 by the desired number of class intervals to arrive at the width of class interval ( i ).  

13. GROUPED FREQUENCY DISTRIBUTION Step 3. Write the lowest score in the set of raw scores as the lower limit in the lowest class interval. Add to this value i – 1 to obtain the upper limit in the lowest class interval. Step 4. The next lower limit can be obtained by adding i to the lower limit of the previous class interval. To get the corresponding upper limit for this class interval, follow step 3 or add i to the preceding upper limit.

14. GROUPED FREQUENCY DISTRIBUTION Step 5. Continue Step 4 until all scores are included in their corresponding class intervals. Step 6. Fill out the f column by following what we have done in the frequency distribution.

15. CUMULATIVE FREQUENCY DISTRIBUTION A cumulative frequency distribution can be obtained by adding the frequency starting from the frequency of the lowest class interval up to the highest class interval. It is also possible to do the reverse, that is if we start to cumulate in the other direction.

16. CUMULATIVE FREQUENCY DISTRIBUTION T he graph of a cumulative frequency distribution is represented by a line graph called an ogive. In graphing the “less than cumulative frequency”, the cumulative frequencies are plotted against the true upper limits or upper class boundaries. While in graphing the “greater than cumulative frequency”, the cumulative frequencies are plotted against the true lower limit or lower class boundaries.

17. STEM – AND - LEAF PLOTS STEP 1. Find the least value and greatest value. STEP 2. Choose appropriate stem value. Write stems vertically with a line to their right. STEP 3. Separate each value into a stem and a leaf by putting the leaves on the plot to the right of the stem. STEP 4. If you want, on a new plot, arrange the leaves so that they are arranged from least to greatest value.