ACTIVITY 7.2.3: Excel: Confidence intervals for a proportion. Click this link to download the spreadsheet for use in this activity. Critical values for quick reference during this activity. Confidence level Critical value 0.90 z" = 1.645 0.95 z* = 1.960 0.99 z* = 2.576 414214 2653565 diddy7 Jump to level 1 A biologist wants to know the highest likely proportion of squirrels in the area that are infected with a particular disease. A random sample of 100 squirrels was tested. Use Sheet 7 of the Excel file linked above to calculate p and the 95% confidence interval. p = Ex: 1.234 # Upper bound for 95% confidence interval = Ex: 1.234 Lower bound for 95% confidence interval = The biologist can say with 95% confidence that the true population proportion of the local squirrel population that is infected with the disease is in the interval [ Ex: 1.234 , Ex: 1.234 ] The highest likely proportion is Ex: 1.234