Knowee
Questions
Features
Study Tools

Powelliphanta, New Zealand's native snails, are among the largest snails in the world. Their weights have a mean of 85 grams and a standard deviation of 6.4 grams.Suppose we repeatedly took random samples of 25 of these snails. What percentage of these samples would we expect to have a sample mean weight between 82.44 grams and 83.72 grams?

Question

Powelliphanta, New Zealand's native snails, are among the largest snails in the world. Their weights have a mean of 85 grams and a standard deviation of 6.4 grams.Suppose we repeatedly took random samples of 25 of these snails. What percentage of these samples would we expect to have a sample mean weight between 82.44 grams and 83.72 grams?

🧐 Not the exact question you are looking for?Go ask a question

Solution

To answer this question, we need to use the Central Limit Theorem (CLT), which states that if we take a large number of random samples from a population, the distribution of the sample means will be approximately normally distributed, regardless of the shape of the population distribution.

First, we need to calculate the standard error (SE), which is the standard deviation of the sampling distribution of the sample mean. The formula for the standard error is:

SE = σ / sqrt(n)

where σ is the population standard deviation and n is the sample size. Substituting the given values:

SE = 6.4 / sqrt(25) = 1.28

Next, we calculate the z-scores for the lower and upper bounds of the weight range (82.44 grams and 83.72 grams). The formula for a z-score is:

Z = (X - μ) / SE

where X is the value from the dataset, μ is the population mean, and SE is the standard error.

For X = 82.44 grams:

Z1 = (82.44 - 85) / 1.28 = -2

For X = 83.72 grams:

Z2 = (83.72 - 85) / 1.28 = -1

Now, we need to find the area under the standard normal curve between these two z-scores. This can be done using a standard normal distribution table or a statistical software or calculator. The values corresponding to Z = -2 and Z = -1 in the standard normal distribution table are 0.0228 and 0.1587 respectively.

The percentage of samples with a mean weight between 82.44 grams and 83.72 grams is the difference between these two areas:

Percentage = (0.1587 - 0.0228) * 100 = 13.59%

So, we would expect approximately 13.59% of the samples to have a sample mean weight between 82.44 grams and 83.72 grams.

This problem has been solved

Similar Questions

Tuatara are rare, medium-sized reptiles found only in New Zealand. Assume female lengths are normally distributed.The length of each tuatara in a sample of 10 female tuatara is measured giving an average length of 48.5cm with a standard deviation of 2.9cm.Suppose we repeatedly took random samples of 10 female tuatara. What percentage of these samples would we expect to have a sample mean weight that is less than 50.34cm?(You should use the empirical rules to estimate this percentage.)Select one:a.2.5%b.100%c.95%d.97.5%

A random sample of 12 items is taken and is found to have a meanweight of 50 grams and a standard deviation of 9 gramsWhat is the mean weight of population1. with 95% confidence2. with 99% confidence

Giant weta, native to New Zealand, are among the largest insects in the world. Their weight is normally distributed with mean of 25 g and standard deviation of 1.9 grams.A random sample of 10 giant weta is obtained. What is the standard error of the sample mean?(Give the answer to 3 decimal places.)

An investigator wants to assess whether the mean (mu) = the average weight of passengers flying on small planes exceeds the FAA guideline of average total weight of 185 pounds (passenger weight including shoes, clothes, and carry-on). Suppose that a random sample of 25 passengers showed an average total weight of 200 pounds with a sample standard deviation of 59.5 pounds. Assume that passenger total weights are normally distributed.What is the value of the test statistic?        Group of answer choicest = 1,8t = 1.50t = 1.65t = 1.26

Weights of women in one age group are normally distributed with a standard deviation of 10.43 kg. A researcher wishes to estimate the mean weight of all women in this age group.Find how large a sample must be drawn in order to be 95% confident (use z=2) that the sample mean will not differ from the population mean by more than 1.30 kg.

1/3

Upgrade your grade with Knowee

Get personalized homework help. Review tough concepts in more detail, or go deeper into your topic by exploring other relevant questions.