# Significant difference help

I have a quick question regarding which statistical test to use to test for a significant difference.

My set of data shows the monthly output of a product for the years between 2013-2017. A new system was put in place in mid-2017 to make the output process more efficient which has led to increased output.

I have calculated the mean output level (units) for each month 2013-2016 and want to compare this to the actual output in 2017.

Which statistical test can I use to show a significant difference for output in the months of June, July, Aug and Sept 2017 which have a higher output level compared to the 2013-2016 average?

Kind regards,

Harvey

• Are you really interested in just testing for a statistically significant difference or a meaningful difference? Would it really be helpful if you found a 0.00001 difference and that was statistically significant? – StatsStudent Jan 6 at 20:15
• Hi there, Thanks for the reply. I was hoping to find a significant difference (p<0.05). I was thinking perhaps a T-Test or an ANOVA test ? – Harvey Jan 6 at 20:32
• Was the supposedly superior new process in place only during May-Aug? Or did it continue from May through the end of the year. // It seems you should make the comparison only for months in which the process was different. – BruceET Jan 6 at 20:37
• Hi there, the process was introduced in May and continued after that. The process aimed to alleviate a backlog of output orders hence the spike. Which statistical test could I use to easily show a sig. difference? – Harvey Jan 6 at 20:47
• Comment continued: With data  old = c(20.25, 20.5, 24.25, 33.75); new = c(87, 48, 52, 44) a one-sided paired t test in R using  t.test(old, new, pair=T, alte="less") returns P-value 3.5%. A one-sample Wilcoxon test on the four differences cannot show a P-value smaller than 5% because there aren't enough pairs. – BruceET Jan 6 at 20:47