A representative sample of trees in a forest shows the trees to have a mean circumference of 19.7 inches and a standard deviation of 1.3 inches. Assuming the circumferences are normally distributed, what is the z-score for a tree with a circumference of 22 inches? a -1.77 b -6.85 c 6.85 d 1.77

Listed in the data table are IQ scores for a random sample of subjects with medium lead levels in their blood. Also listed are statistics from a study done of IQ scores for a random sample of subjects with high lead levels. Assume that the two samples are independent simple random samples selected from normally distributed populations. Do not assume that the population standard deviations are equal. Complete parts (a) and (b) below. Click the icon to view the data table of IQ scores. a. Use a 0.05 significance level to test the claim that the mean IQ scores for subjects with medium lead levels is higher than the mean for subjects with high lead levels. What are the null and alternative hypotheses? Assume that population 1 consists of subjects with medium lead levels and population 2 consists of subjects with high lead levels. X A. Ho: H₁ H₂ H₁ H₁ H₂ c. Ho: M₁ = H₂ H₁: H₁ H₂ The test statistic is 0.56. (Round to two decimal places as needed.) The P-value is (Round to three decimal…

The goal of the one-sample t-test is to: Group of answer choices describe the location of a score within a distribution compare the mean of a sample to the population mean. compare the means of two samples. compare the standard deviation of a sample to the standard deviation of the population.

The speed vehicles traveled on a local highway was recorded for one month.  The speeds ranged from 47 mph to 62 mph with a mean speed of 55 mph and a standard deviation of 6 mph.  The quartiles and median speeds were 50 mph, 59 mph, and 52 mph.  Suppose increased patrols reduced speeds by 7%.  Find the new mean and standard deviation. Express your answer in exact decimals. Choose the best answer below:  A. Mean: 3.85 mph, SD: 0.42 mph B. Mean: 58.85 mph, SD: 6.42 mph C. Mean: 51.15 mph, SD: 6 mph D. Mean: 58.85 mph, SD: 6 mph E. Mean: 51.15 mph, SD: 5.58 mph

Scores on in biology tests are normally distributed with the mean of 78 in a standard deviation of 8.2 find the score that represents the 61st percentile

A company produces steel rods. The lengths of the steel rods are normally distributed with a mean of 122.7-cm and a standard deviation of 0.5-cm.Find P15, which is the length separating the shortest 15% rods from the longest 85%.P15 = -cm