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Ch. 5 - Normal Probability Distributions
Larson - Elementary Statistics: Picturing the World 8th Edition
Larson8th EditionElementary Statistics: Picturing the WorldISBN: 9780137493470Non è quello che usi tu?Cambia libro di testo
Capitolo 5, Problema 5.3.39

Bags of Baby Carrots The weights of bags of baby carrots are normally distributed, with a mean of 32 ounces and a standard deviation of 0.36 ounce. Bags in the upper 4.5% are too heavy and must be repackaged. What is the most a bag of baby carrots can weigh and not need to be repackaged?

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Identify the key parameters of the normal distribution: the mean (μ = 32 ounces) and the standard deviation (σ = 0.36 ounces). The problem asks for the maximum weight a bag can have and not be in the upper 4.5% of the distribution.
Determine the z-score corresponding to the upper 4.5% of the normal distribution. Since the upper 4.5% corresponds to the top tail of the distribution, find the z-score for the cumulative probability of 1 - 0.045 = 0.955 using a z-table or statistical software.
Use the z-score formula to relate the z-score to the weight (X): z = (X - μ) / σ. Rearrange this formula to solve for X: X = μ + z * σ.
Substitute the known values into the formula: μ = 32, σ = 0.36, and the z-score obtained in the previous step. This will give the maximum weight a bag can have without being in the upper 4.5%.
Interpret the result: The calculated weight represents the threshold above which bags are considered too heavy and must be repackaged.

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Normal Distribution

Normal distribution is a probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean. It is characterized by its bell-shaped curve, defined by its mean and standard deviation. In this context, the weights of bags of baby carrots follow a normal distribution, which allows us to use statistical methods to determine probabilities and thresholds.
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Z-Score

A Z-score is a statistical measurement that describes a value's relationship to the mean of a group of values. It is calculated by subtracting the mean from the value and then dividing by the standard deviation. In this scenario, the Z-score will help identify the weight threshold above which the top 4.5% of bags fall, indicating the maximum weight a bag can have without needing repackaging.
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Percentiles

Percentiles are measures that indicate the value below which a given percentage of observations in a group of observations falls. For example, the 95th percentile is the value below which 95% of the data points lie. In this question, we need to find the weight corresponding to the 95th percentile to determine the maximum weight a bag can have before it is considered too heavy.
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