## Task – Global Homework Experts

__Task 1 experiment with the files in the week 3 lecture sectiongenerate random samples and summarize them __

__Question 1__

Based on the screen shot below

- What the excel function =COUNTIF(B5#,”yes”) return (what is the output)
- What the excel function =COUNTA(B5#) return (what is the output)
- Using the answer to part A) and Part B) to calculate the sampling population proportion

Note discussion of sampling populations is given in the video

note that video will start playing at time 380s if you watch from I start with a totally blank worksheet and make samples using the screenshot above

Answer

Note that there is a blue rectangle around the cell range B5:B9 so B5# refers to the cell range

B5:B9

A) 4 yes

B) there are 5 non empty cells in the array B5#

C) sampling population proportion 4/5=0.8

Question 2

*If you use B6# as a sampling population what is the population proportion of yes *

Answer

Population proportion p=54882/100000= 0.54882

Question 3

If you consider all of F7# as a single sample what is the sample proportion of yes

Answer

Sample proportion

Question 4

If you consider all of F7# as a single sample what is the sample proportion of yes

Answer

Sample proportion

__General understanding of a measures of central tendency (the mean ) and a measure of spread (the standard deviation) __

- What the sample size
*n*, sample mean and sample standard deviation s of the sample

Report Mark out of 20 |

7 |

13 |

10 |

Answer you have quantitative variable size *n*=3

Sample average (mean)

Sample standard deviation

- Given the 4 samples of data below and answer the following questions without formula (the answer is obvious and you don’t need the formula if you understand that standard deviation measures how far the points are from the average)

Sample 1: 100 100 100

Sample 2: 50 100 150

Sample 3: 90 100 110

Sample 4: 200 200 200

- What is the mean of Sample 1
- What is the standard deviation of Sample 1
- Compare the mean and standard deviation of Sample 1 and Sample 2
- Compare the mean and standard deviation of Sample 1 and Sample 4

Answer: mean of sample 1 is 100 and the standard deviation is 0

Sample 1 and 2 have the same mean but sample 2 must have a higher standard deviation,

Sample 1 and sample 2 have the same spread (standard deviation is 0) however sample 2 has a higher mean

- If 80 out of 100 Australians are scared of Donald Trump what is the sample proportion

Answer =80/100=0.8

As simpler example

If I ask 5 people if they are scared of Donald Trump and the answers are the following dataset with 1 categorical variable

Are you scared of trump ? |

Yes |

Yes |

No |

Yes |

No |

You cannot find average but the proportion that are scared 3/5=0.6

Answer 0.05*200=10

5% 5 per cent 5/100=0.05

Harder Multiple choice

question 1

- The heights of 100,000 females have heights summarized by the following histogram

The distribution of heights is symmetric with mean 175 and median 175

(the mean and median must be the same because it is symmetric)

How many females have a height between 165 and 185

A)8,400 B)7,000 C)2,000 D)1,0000

ANSWER A)

The blue section must be 8% (the average is an axis of symmetry for the graph)

so the middle section is 100%-8%-8%=84% 84% of 10,000 is 8,400

Question 2

Complete the following table

Height X | round(height/5,0)*5 Height rounded to the nearest 5 |

174 | 175 |

182 | 180 |

183 | 185 |

187 | 185 |

168 |

Multiples of 5 are 0,5,10,15,20,25

Multiple choice fill in the blank

A)195

B)165

C)170

D)None of the above

Answer C

170

168 is between 165 and 170 but it is closer to 170

mround(height,5) will round height to the nearsest multiple of 5

The multiples of 5 are 0,5,10,15,20,