Refer to the following frequency distribution for Questions 1, 2, 3, and 4.
The frequency distribution below shows the distribution for suspended solid concentration (in ppm) in river water of 50 different waters collected in September 2011.
Concentration (ppm) Frequency
20 - 29 1
30 - 39 8
40 - 49 8
50 - 59 6
60 - 69 16
70 - 79 7
80 - 89 2
90 - 99 2
Q1. What percentage of the rivers had suspended solid concentration less that 50?
Q2. Calculate the mean of this frequency distribution.
Q3. In what class interval must the median lie? Explain your answer. (You don't have to find the median)
Q4. Assume that the largest observation in this dataset is 98. Suppose this observation were incorrectly recorded as 988 instead of 98. Will the mean increase, decrease, or remain the same? Will the median increase, decrease or remain the same? Explain your answers.
Refer to the following information for Questions 5 and 6.
A coin is tossed 4 times. Let A be the event that the first toss is heads. Let B be the event that the third toss is heads.
Q5. What is the probability that the third toss is heads, given that the first toss is heads?
Q6. Are A and B independent? Why or why not?
Refer to the following data to answer questions 7 and 8. Show all work. Just the answer, without supporting work, will receive no credit.
A random sample of song playing times in seconds is as follows: 242 231 220 213 230 293
Q7. Find the standard deviation.
Q8. Are any of these playing times considered unusual in the sense of our textbook? Explain. Does this differ with your intuition? Explain.