Business Statistics Assignment: Confidence Interval Analysis and Bias

This business statistics assignment analyzes an opinion poll conducted by the Pew Research Centre regarding US tariffs. The solution calculates a 95% confidence interval for the proportion of respondents in favor of the tariffs, using the provided survey data, sample size, and standard error. The assignment compares the calculated confidence interval with one derived from the poll's margin of error, highlighting potential differences and discussing potential biases, such as selection bias and biases introduced by the sponsoring authority's orientation. The assignment provides references to relevant statistical methods in business research, emphasizing the importance of understanding and addressing biases in data analysis and interpretation. This comprehensive analysis helps students grasp the practical application of confidence intervals and the critical evaluation of survey results.

BUSINESS STATISTIC
STUDENT ID:
[Pick the date]

1) An opinion poll was conducted by Pew Research Centre nationally between July 11 and
July 15, 2018 regarding the merit of the increased tariffs being levied by US on various
trading partners. The results of this survey can be obtained from
http://www.pollingreport.com/trade.htm
The poll question is indicated follows.
“Overall, do you think these increased tariffs between the U.S. and its trading partners will be
good or bad for the United States?"
2) The results of the survey are summarised as below.
40% of the respondents opined that the tariffs applied by the US on the trading partners will
be good for USA.
49% of the respondents opined that the tariffs applied by the US on the trading partners will
be bad for USA.
11% of the respondents were unsure of their opinion on the impact of the tariffs imposed on
the trading partners for USA.
3) The obtaining of the requisite confidence interval can be facilitated by adding and
subtracting the margin of error.
Thus, confidence interval for proportion of people who are in favour of tariffs on other
trading partners would be (40%-3.7%, 40%+3.7%) i.e. (36.3%, 43.7%).
It may be estimated that the average proportion of population who is in favour of levying of
tariffs on the trading partners would lie between 36.3% and 43.7% (Flick, 2015).
4) The confidence interval can be computed using the given data for the sample.
Mean proportion of those who are in favour = 0.40

Sample size = 1007
Standard error = √((0.4)*(1-0.4)/1007) = 0.0154
Since the confidence level is 95%, hence the z level corresponding to this confidence level
would be 1.959 (Hillier, 2016).
Thus, lower level of 95% confidence interval = 0.4 -1.959*0.0154 = 0.3697 or 36.97%
Upper level of 95% confidence interval = 0.4 + 1.959*0.0154 = 0. 43.03%
5) The calculated confidence interval is (36.97%, 43.03%). This is slightly different from the
confidence interval which has been derived based on the poll data margin of error. The
potential difference between the two values can be on account of the presence of potential
biases (Eriksson & Kovalainen, 2015).
6) The given study might be influenced by a host of biases which need to be indicated. One
of the first ones would be the selection bias which relates to the process involved in obtaining
the sample which may have led to a sample which is not representative of the underlying
population of interest. Additionally, the underlying sampling technique is not known which
can also potentially be a source of bias since the key attributes of the population may not be
well represented in the sample. Additionally, the orientation of the sponsoring authority may
have influenced the underlying methods deployed and may be the result in order to serve
vested interests which may have also introduced bias in the results obtained from the survey
(Hair, Wolfinbarger, Money, Samouel & Page, 2015).

References
Eriksson, P. & Kovalainen, A. (2015) Quantitative methods in business research. 3rd ed.
London: Sage Publications.
Flick, U. (2015) Introducing research methodology: A beginner's guide to doing a research
project. 4th ed. New York: Sage Publications
Hair, J. F., Wolfinbarger, M., Money, A. H., Samouel, P., & Page, M. J. (2015) Essentials of
business research methods. 2nd ed. New York: Routledge.
Hillier, F. (2016) Introduction to Operations Research. 6th ed. New York: McGraw Hill
Publications.