Zero error in an instrument introduces

In five successive measurements, the mass of a ball is measured to be $2.61 \,g, 2.58 \,g, 2.40 \,g, 2.73 \,g$ and $2.80 \,g$. The mean absolute error in the measurement is (in $\,g$)

The period of an oscillating simple pendulum is $T = 2 \pi \sqrt{\frac{\ell}{g}}$,where the length $\ell = 100 \text{ cm}$ with an error of $1 \text{ mm}$. The period $T = 2 \text{ s}$. The time for $100$ oscillations is measured by a stopwatch with a least count of $0.1 \text{ s}$. The percentage error in the gravitational acceleration $g$ is: (in $\%$)

Time intervals measured by a clock give the following readings: $1.25 \; s, 1.24 \; s, 1.27 \; s, 1.21 \; s$,and $1.28 \; s$. What is the percentage relative error of the observations?

$A$ student determined Young's Modulus of elasticity using the formula $Y = \frac{M g L^{3}}{4 b d^{3} \delta}$. The value of $g$ is taken to be $9.8 \, m/s^2$, without any significant error. His observations are as follows:

Physical Quantity	Least count and Observed value
Mass $(M)$	$1 \, g$ and $2 \, kg$
Length of bar $(L)$	$1 \, mm$ and $1 \, m$
Breadth of bar $(b)$	$0.1 \, mm$ and $4 \, cm$
Thickness of bar $(d)$	$0.01 \, mm$ and $0.4 \, cm$
Depression $(\delta)$	$0.01 \, mm$ and $5 \, mm$

Then the fractional error in the measurement of $Y$ is:

In a simple pendulum experiment for determination of acceleration due to gravity $(g)$, time taken for $20$ oscillations is measured by using a watch of $1\,s$ least count. The mean value of time taken comes out to be $30\,s$. The length of the pendulum is measured by using a meter scale of least count $1\,mm$ and the value obtained is $55.0\,cm$. The percentage error in the determination of $g$ is close to ........... $\%$