Statistics

Need to show work (#1-8)

1) The following frequency distribution table lists the time (in minutes) that participants were late for an experimental session. Compute the sample mean, median, and mode for these data.

mean	min
median	min
mode	min

Time (min)	Frequency
0	3
2	5
3	2
7	1
8	2

2) A neuroscientist measures the reaction times (in seconds) during an experimental session in a sample of cocaine-addicted 

(n = 8),

 morphine-addicted 

(n = 12),

 and heroin-addicted rats 

(n = 6).

 Mean reaction times in each sample were 14, 12, and 16 seconds, respectively. What is the weighted mean for all three samples? Hint: The overall mean is not 14.0seconds. (Round your answer to two decimal places.)  sec

3) A researcher measures the time (in seconds) it takes a sample of five participants to complete a memory task. It took four of the participants 3, 4, 4, and 5 seconds. If 

M = 5,

 then what must be the fifth time recorded?  sec

4) An expert reviews a sample of 10 scientific articles 

(n = 10)

 and records the following number of errors in each article: 0, 3, 8, 1, 3, 7, 4, 9, 3, and 2. Compute SS, variance, and standard deviation for this sample using the definitional and computational formula. (Round your answers to two decimal places.)

SS
variance
standard deviation		errors

5) A professor records the time (in minutes) that it takes 16 students to complete an exam. Compute the SS, the variance, and the standard deviation assuming the 16 students constitute a population and assuming the 16 students constitute a sample. (Round your answers for variance and standard deviation to two decimal places.)

27	41	40	46
56	22	35	31
50	34	49	43
27	29	42	16

(a) the 16 students constitute a population

SS
variance
standard deviation		min

(b) the 16 students constitute a sample

SS
variance
standard deviation		min

6) To study bonding between mothers and infants, a researcher places each mother and her infant in a playroom and has the mother leave for 10 minutes. The researcher records crying time in the sample of infants during this time that the mother was not present and finds that crying time is normally distributed with 

M = 8

 and 

SD = 1.1.

 Based on the empirical rule, state the range of crying times within 68% of infants cried, 95% of infants cried, and 99.7% of infants cried.

(a) 68% of infants cried  to  min (b) 95% of infants cried  to  min (c) 99.7% of infants cried  to  min

7) Based on the empirical rule, what percentage of data fall within 1 SD, 2 SD, and 3 SD of the mean for data that are distributed normally? (Enter your answers to one decimal place.)

% of all scores lie within 1 SD of the mean

% of all scores lie within 2 SD of the mean

% of all scores lie within 3 SD of the mean

8) A social scientist measures the number of minutes (per day) that a small hypothetical population of college students spends online.

Student	Score	Student	Score
A	88	F	94
B	91	G	99
C	88	H	54
D	27	I	83
E	79	J	94

(a) What is the range of data in this population?  min (b) What is the IQR of data in this population?  min (c) What is the SIQR of data in this population?  min (d) What is the population variance?   (e) What is the population standard deviation? (Round your answer to two decimal places.)  min