# Stats Ch 7

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question
Identify which of the following is not a property of the standard normal curve.
It has inflection points at ?Â±2?.
question
The standard normal probability distribution has a mean of? _______ and a standard deviation of? _______.
zero, one
question
Determine whether the following graph can represent a normal density function. Can this graph represent a normal density function?
yes
question
Determine whether the following graph can represent a normal density function.Could the graph represent a normal density? function?
no
question
The relative frequency histogram represents the length of phone calls on? George's cell phone during the month of September. Determine whether or not the histogram indicates that a normal distribution could be used as a model for the variable.
yes because the histogram has the shape of a normal curve
question
One graph in the figure represents a normal distribution with mean ?=16 and standard deviation ?=3. The other graph represents a normal distribution with mean ?=9 and standard deviation ?=3. Determine which graph is which and explain how you know.
Graph A has a mean of mu?equals=9 and graph B has a mean of mu?equals=16 because a larger mean shifts the graph to the right.
question
If the area under the standard normal curve between zequals=minus?1.46 and zequals=0 is? 0.4279, then what is the area under the standard normal curve between zequals=0 and zequals=?1.46?
Due to the symmetry of the standard normal? curve, the area between zequals=0 and the given negative? z-value will be the same as the area between zequals=0 and the same positive? z-value. 0.4279
question
If the area to the left of a? z-score is less than? 0.5, what must be? true?
The? z-score must be negative.
question
If the area to the left of a? z-score is greater than? 0.5, what must be? true?
The? z-score must be positive.
question
Find the? Z-scores that separate the middle 41?% of the distribution from the area in the tails of the standard normal distribution.
-.54, .54 1) 1-.41=.59 2).59/2=.295 3) -.295 z score=-.54
question
A study was conducted that resulted in the following relative frequency histogram. Determine whether or not the histogram indicates that a normal distribution could be used as a model for the variable.
The histogram is not? bell-shaped, so a normal distribution could not be used as a model for the variable.
question
Find the area under the normal curve to the left of -3 and 3.
1) 3=.99865 2)-3=.00135 3) 1-(.99865-.00135)
question
P(x>38) mean=50 stdv=7
=(x-mean)/standard deviation 1)=-1.714 2)z score =.04363 3) 1-.04363=.9564 or stat crunch
question
Assume that the random variable X is normally? distributed, with mean ?=62 and standard deviation ?=10. Compute the probability ?P(56
stat crunch-stat-calc-normal
question
The mean incubation time of fertilized eggs is 22 days. Suppose the incubation times are approximately normally distributed with a standard deviation of 1 day. ?(a) Determine the 19th percentile for incubation times. ?(b) Determine the incubation times that make up the middle 39?%.
a) stat crunch-stat-calc-normal mean=22 stdv=1 and =.19 =21 b) look at stat crunch chart and put middle
question
Find the area of the shaded region. The graph to the right depicts IQ scores of? adults, and those scores are normally distributed with a mean of 100 and a standard deviation of 15.