Chapter 6: Problem 26
Find the following:
a. \(\quad P(-3.05
Short Answer
Expert verified
a. 0.4989, b. 0.9073, c. 0.0150, d. 0.0074
Step by step solution
01
Find the probability for a. \( P(-3.05
First, lookup the z-score for -3.05 in a standard Z-table, which gives 0.0011. This means that 0.0011 (or 0.11%) of the distribution falls to the left of -3.05. Because \(z<0.00\) represents the left half of the entire normal distribution, it represents 0.50 (or 50%) of the distribution. So, to find \(P(-3.05<z<0.00)\), subtract the Z-table value of -3.05 from 0.5: \(0.5 - 0.0011 = 0.4989\)
02
Find the probability for b. \(P(-2.43
First, lookup Z-table values for both -2.43 and 1.37 which are 0.0074 and 0.9147 respectively. To find the probability, subtract the smaller Z-table value from the larger one: \(0.9147 - 0.0074 = 0.9073\).
03
Find the probability for c. \(P(z
Lookup the z-score for -2.17 in a standard Z-table. The result is 0.0150 which directly provides the required probability as it falls to the left of -2.17.
04
Find the probability for d. \(P(z>2.43)\)
Lookup the z-score for 2.43 in a standard Z-table, which gives 0.9926. The required probability falls to the right of 2.43. Since the total probability is 1, subtract the Z-table value from 1 to get the probability: \(1 - 0.9926 = 0.0074\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Z-Score
The Z-score is an essential concept in statistics, especially when dealing with the standard normal distribution. It represents how many standard deviations a data point is from the mean of the distribution. To calculate a Z-score, you use the formula:\[ Z = \frac{X - \mu}{\sigma} \]where:
- \(X\) is the value you are evaluating.
- \(\mu\) is the mean of the distribution.
- \(\sigma\) is the standard deviation of the distribution.
Probability Calculation
Probability calculation in the context of the standard normal distribution helps us understand the likelihood of a Z-score falling within a certain range. We are typically interested in:
- The probability of a Z-score being less than a particular value.
- The probability of a Z-score being greater than a particular value.
- The probability of a Z-score falling between two values.
Z-Table Lookup
The Z-table is a tool used to find the cumulative probability associated with a Z-score. This table gives the probability that a standard normal random variable is less than a certain value. To use the Z-table:
- Locate the Z-score in the table's row and column (usually represented by tenths and hundredths).
- Find the intersection that gives the cumulative probability.