Chapter 6: Problem 33
Find the probabilities for each, using the standard normal distribution. \(P(z< -1.51)\)
Short Answer
Expert verified
The probability \(P(z < -1.51)\) is approximately 0.0655.
Step by step solution
01
Understand the Standard Normal Distribution
The standard normal distribution, also known as the Z-distribution, is a normal distribution with a mean of 0 and a standard deviation of 1. We use the Z-table to find probabilities associated with z-scores.
02
Interpret the Problem
The problem asks for the probability that the z-score is less than -1.51. This is denoted as \(P(z < -1.51)\).
03
Use the Z-table
Locate the z-score of -1.51 in the Z-table. The Z-table gives us the cumulative probability from the far left up to the z-score. The standard Z-table shows probabilities for z-scores less than a specific value, which matches our requirement.
04
Read the Z-table Value
In the Z-table, find the row for -1.5 and the column for 0.01. The intersection of these gives the probability \(P(z < -1.51)\). This value is approximately 0.0655.
05
Record the Probability
The probability \(P(z < -1.51)\) is approximately 0.0655. This means that approximately 6.55% of the data falls below a z-score of -1.51 in a standard normal distribution.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding the Z-Score
The z-score is a crucial concept in statistics, representing the number of standard deviations a data point is from the mean. In the context of the standard normal distribution, a z-score allows us to understand how extreme a value is compared to the average. Whenever we talk about probabilities in a standard normal distribution, we're essentially dealing with z-scores.
- A positive z-score indicates a value above the mean.
- A negative z-score indicates a value below the mean.
- Z-scores are dimensionless since they're derived from a ratio.
What is Cumulative Probability?
Cumulative probability is the likelihood that a random variable is less than or equal to a particular value. When using the standard normal distribution, this involves summing the probabilities from the left end of the distribution up to a specific z-score. This cumulative aspect allows us to determine how much of the data falls below a specific point.
- It's useful for understanding the proportion of data below a certain value.
- In our example, it helps us find the probability that a z-score is less than -1.51.
- Cumulative probabilities range from 0 to 1.
Navigating the Z-Table
The Z-table is a fundamental tool in statistics for finding probabilities related to the standard normal distribution. It provides the cumulative probability of z-scores and is structured to be user-friendly once you understand how it works.
To use the Z-table effectively:
- Identify the z-score you're interested in (e.g., -1.51).
- Decipher the table by locating the row and column corresponding to your z-score. Rows typically correspond to the z-score's whole and tenths’ parts, while columns represent the hundredths.
- The intersection of these row and column gives the cumulative probability for that z-score.