To find the first quartile (Q1) for the given test scores, we'll follow these steps:
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Order the data from least to greatest.
- The test scores are: 25, 35, 45, 50, 60, 80, 90, 95, 100.
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Determine the position of Q1:
- The first quartile (Q1) is the median of the first half of the data. Since there are 9 students, the median is the 5th score in the ordered list.
- The scores are: 25, 35, 45, 50, 60, 80, 90, 95, 100
- The first half of the data set consists of the first 4 scores: 25, 35, 45, 50.
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Calculate Q1:
- To find Q1, we find the median of the first half (25, 35, 45, 50).
- The median of these 4 scores is the average of the 2nd and 3rd values: (35 + 45) / 2 = 40.
Thus, the value of the first quartile (Q1) for this data set is 40.