The Mental Development Index (MDI) is a measure used in observing infants over time. Suppose MDI scores are approximately normally distributed with a mean of 105 and a standard deviation of 15. Which of the following is a true statement? Approximately 95% of all MDI scores are between 90 and 120. An infant with a MDI score of 135 would be farther away from the mean than an infant with a standardized MDI score of -2.25 O An infant with a MDI score of 125 would be at a higher percentile than an infant with a z-score of 2 An infant with a MDI core of 120 would be at the 84th percentile. Approximately 84% of all MDI scores are less than 90

A study by the National Center for Health Statistics suggested that women between the ages 20 and 29 in the US have a mean BMI of 26.8 with a standard deviation of 7.4. A BMI of 30 or greater is considered as being obese. What proportion of women in this age range are obese?

The Wechsler IQ test is normally distributed with mean 100 points and standard deviation 15 points. Andy Warhol was found to have an IQ of 86 on the Wechsler IQ test. What was his z-score, and what does it mean?​ ​

Suppose that Jett achieves a score of 1250 on the SAT, and his sister Kate scores 29 on the ACT. The SAT scores are normally distributed with a mean of 1100 and standard deviation of 250. The ACT scores are normally distributed with a mean of about 20 and standard deviation of 5. Who did better, relative to their peers?

in a test of a lifelong brand of tires , a survey revealed that the mean life was 35,000 mikes and the standard deviation was 7083 mikes.  if the shape of the population distribution is known to be normal, approximately what percentage of the tires lasts less than 20834 miles ?

An article in the San Jose Mercury News stated that students in the California state universitysystem take 4.25 years, on average, to finish their undergraduate degrees. Suppose you believe that the mean time is longer. You conduct a survey of 64 students and obtain a sample mean of 4.5 with a sample standard deviation of 1.5. Do the data support your claim at the 1% level?

Solar energy is considered by many to be the energy of the future. A recent survey was taken to compare the cost of solar energy to the cost of gas or electric energy. Results of the survey revealed that the distribution of the amount of the monthly utility bill of a three-bedroom house using gas or electric energy had a mean of $117 and a standard deviation of $13. If the distribution can be considered normal: Approximately what percentage of homes will have a monthly utility bill less than $78? Note: Do NOT include the "%" sign Do NOT round any decimals, if applicable

Average adult Americans are about one inch taller but nearly a whopping 25 pounds heavier than they were in 1960, according to a report from the Centers for Disease Control and Prevention (CDC).  City A is considered one of America's healthiest cities.  Is the weight gain since 1960 similar in city A? A sample of n=25 adults suggested a mean increase of 22 pounds with a standard deviation of 9.4 pounds.  Is City A significantly different in terms of weight gain since 1960? Complete and interpret 5 step hypothesis testing by hand at a 5% level of significance using a Z-test.  Show each step and your work.

The college physical education department offered an advanced first aid course last summer. The scores on the comprehensive final exam were normally distributed, and the z-scores for some of the students are shown below. Robert 1.05 Juan 1.51 Haley −1.95 Joel 0.00 Jan −0.67 Linda 1.57 (a) If the mean score was ? = 151 with standard deviation ? = 16, what was the final exam score for each student?

The distribution of the amount of money spent by first-time gamblers at a major casino in Las Vegas is approximately normal in shape with a mean of $600 and a standard deviation of $120. According to the standard deviation rule, almost 84% of gamblers spent more than what amount of money at this casino?